■ sHHli 







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■ 



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■ ■ m 

SI 
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in 



1- ^1- 




KDUCATIOXAL R 

rll's Map-l>ra\* in- ( urtl*. 
t Out lint' Maps. 

i ». < )M*% I \. i-< Im Book* 

- Stud) « • t 
■ li.in. I'- Natural IMiilonnphy. Hv .1 F«»ur r.irt- 

fleoton*i Hlstorj «»t the i niied state-. 

I rOfOtt*! OotllBOl Of Vitural rhili>Hi>|ih\ . 

! ,lu. ti i-.ii Of Man. N. Ihiniws 

'1 Treatise on sur\< 
BQoaoro*! BogVsli LoogoofQ .m<i Utorotoro* 



I >r.i\\ 1 11 1^ ( .ir.U. 

iwooo?i Prloolploi «>i I duoottoo i'i i.ii..iii\ Lppllod* 
i-tniN Bftatorl* «i Boforonoc Book 

BoOOlow'* Hot :uii« .tl (harts. Wilh Km - i- ior Supp. >rter. 

■koon Prtaaora. M L 

(OOO'l I rror* In the l**»«' of Kii^linh. :i<>n. 

Holder'* I h mt'iits «>f Zool< . 
Huxli Voumauo's I'hyslolOgJ ;Um If Jf^lOMIOi 

^ »t n i.ii 1 1 i-t i>r \ Boodora ; 

II. Priondi in Paatbi 
[] 

boors with 
Cfcv :<i. 

• Iiihn inn »t '-. II i-tori. il I 

I \ : . 
V 

. I < » I 1 « . 1 1 J 1 < » r ' * < . « < . -r . » J . 1 1 

Sentence ;m.i \\<>i.i Book* 

Prloolploi 1 1 1 1 • 1 • ' ' ■ ' 1 1 1 • of 1 • • 1 1 1 1 1 ■ 1 ■ 

Johonnot m.i r. . 1 1 1 • • 1 1 ' « 1 1 • nv Btorj Pbytlolof 

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■ Ponpoctlre Serle*. " rmal. 

- ivpoJoi 

■ DmwinK Tablet*. 

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Outline and Kelirf lh- Itooki 

Mrrhnnlral I okf 

ArchliertMi.il Mr.ivi lag, -Book*. 

it« <.f I'd < onomy. 

Mudi i»f 

Mil. BOl Krono.nv. 



A CLASS-BOOK 



OF C.1I E \L I 8TEY 



FOR THK L>K OF SCHOOLS AND COLLEGES 
AND FOR POPULAB HEADING 






BDW \IM> I..' rOXTMANS, It D. 



THIRD BDITIOy, RBTISKD wi» PAETL1 Rl 

Bi WILLIAM .1. jTOUMANS, M. I>. 

■U3BS1 MAN-"s F 







EtK 
A PPLE M PA 

K88I 









Copyright, 1863, 1875, 1889. 
By D. APPLETON AND COMPANY. 



PB EFACE 



The " ( 'lass-Book of ( iiemistry n was first published 
in L851, and waa designed as a popular introduction to 

The aim of the work 

athor was "to present the subject in such 

win the attention and engage the inter- 

and it was "especially adapted to the 

oth in and ont of school who 

something of this interesting Bci« 

sore Dor opportunity to pursue 

it in [led and experimental way." 

lizr thic r the plan of the work was 

. thai <>f the usual text-hook hv omitting 

descriptions of the lea important suh>tanees. such as 

netals and compounds, and all discussion of 

pur imcal q - thai are of interest only to 

and the original investigator. 

• all hut the simples! experim< i 

■ out. as >ucli particulars can be of little 

• »k that will find it- n 

ind a laboratory irly 

alv. uting. In this way room was obtained for 

the explan 1 principles and a fuller 

Bpp nd fiiiniliar :i iV.tirs 

imon life in which all are interested than in 



jy PREFACE. 

customary in the ordinary text-book. Freeing the 
subject as far as possible from technicalities and pre- 
senting its facts and laws in a terse and simple style, 
the author was enabled to adapt the work to the 
wants of the general reader, as well as to class-room 
study. 

The book was rewritten and somewhat extended on 
the same general plan in 1863, and was again revised 
and brought down to date, but without material varia- 
tion in the manner of presenting the subject, in 1875. 
That the plan thus adhered to from the first was a good 
one, and well suited to educational needs, is shown by 
the fact that the book has always been a favorite with 
beginners in the science, more than one hundred and 
forty-five thousand copies of the several editions having 
been sold. A happy faculty for the popular exposition 
of science was possessed by the author to a remarkable 
degree. Much of the popularity of the " Class-Book " 
was undoubtedly won by the vivid style and enthusias- 
tic tone which he gave to the work, and which so light- 
ened the labor of study as to make it a pleasure. 

In preparing the present revision, made necessary 
by the advances of the science in recent years, the aim 
has been to follow as closely as possible the guiding 
idea of preceding editions, retaining the original form 
of statement in all cases where the growth and ac- 
ceptance of later views did not compel a change, and 
giving prominence to those practical applications of 
chemical knowledge of which the last quarter of a cent- 
ury has been so remarkably fruitful. 

Part I, " Chemical Physics," has been much short- 
ened by omitting all portions that had no direct bearing 
upon the chemical laws and phenomena presented in this 
volume. The purely physical aspects of matter and force 



v 

have been left to the text-books of natural philosophy, 
deb pupils generally go through before beginning 
chemistry. That is where these subjects 
properly belong and are always treated. Their intro- 
duction into chemistry involves a repetition of topic- in 
two bi of Btudy, and, in a volume of mod- 

it crowds out much useful matter which 
_:it on i iint to be spared. A knowledge of 

ie, important to the chemical stu- 
\t, as i> a know) arithmetic, but in both cases 

it i! Lined that the knowledge is already gained. 

In ; i subject to it- appropriate teacher, the 

no of our latest and best authorities has 
lowed. 
The most important changes in Part TI. "Chemical 
e introduction of the Periodic or Men- 
del M<>n of the element- an<l a new mode 
col stitution of acid-, bases, and Baits. 

faction in Part I has been more than made up 

by ■ and other new matter which 

introduced in Tart III. " Descriptive I hem- 
fa this expansion pre has be n given to 
deal applic and illustrations of the principles 
. in order to show the pupil how chemis- 
try initio— ,ttTair> of his daily life. By 
Ie to regard it as an ever-present 
fluence ing the operations of 
i the processes of the arts, instead of a mass 
Irv and The 

foments has been changi d to conform 

• •• ( 

I impound trmer field 

I " has been entirely rewritten, and ba bet d 

ijii; 



v i PREFACE. 

chemical relations and practical properties that have 
been discovered in these substances, 

I take pleasure in acknowledging my obligations to 
the great work of Roscoe and Schorlemmer, which has 
been followed in preparing the division on the Carbon 
Compounds, and to Tidy's excellent u Handbook of 
Modern Chemistry" for many valuable practical sug- 
gestions. I am also greatly indebted to my friend Mr. 
Frederik A. Fernald for valuable assistance in the 
work of revision^ both in the preparation of the new 
matter and in seeing the pages through the press. 

W. J. Y. 

New York, October 1, 1889, 

*% The cross-reference numbers in the text refer 
to paragraphs. 






CON T E N T 8 



1 

PART I. 
CHEMICAL PHT8IC8. 

I I! \1T1 K i 

um it- Mi nt . 

CHAPTER [1 

ITY G 

CHAFTKB III. 

HOU HON. 

$ 1. Minute <*"n-titi • IS 

1 l 

1 3. 1') 

§4. Crystallizat; n . ....... 

OHAPTEB iv. 

• T \M> < in MI- \I. * IT \" 

1 1. Thermal E 

f 2. Changes b Matt, r 

. . 

I H \'i I i: v. 
.Ni) Cum } 

QB \rn.i: vi. 
QHAF1 i i: vn 



viii CONTENTS. 

PAGE 

§ 3. Dark Lines in the Spectrum . 54 

§ 4. Spectroscopic Applications 58 



PART II. 

CHEMICAL PEINCIPLES. 

CHAPTER VIII. 
Geneeal Character of Chemical Action 63 

CHAPTER IX, 
THEORETICAL chemistry, 

§ 1. Theory of Atoms and Molecules . 



§ 2. Progress of Chemical Theory 

§ 3. Theory of Atomicity and Quantivalence 

§ 4. Theory of Radicals .... 

§ 5. Theory of Acids, Bases, and Salts 

§ 6. Theory of Isomerism and Allotropism . 

§ 7. Theory of combining Volumes 



73 

75 
82 
83 
88 
91 



CHAPTER X. 

Atomic Weights and the Properties of Elements ... 95 

CHAPTER XL 
The Chemical Nomenclature ........ 101 



PART III. 

DESCRIPTIVE CHEMISTRY, 

CHAPTER XII. 
Hydrogen . • 107 

division i. — non-metals. 

CHAPTER XIII. 

the halogens. 

§ 1. Fluorine ... 114 

§ 2. Chlorine 116 

§ 3. Bromine 123 

§ 4. Iodine 125 

CHAPTER XIV. 
TBITALENT non-metals. 

§ 1. Nitrogen . 126 

§ 2. Phosphorus 136 



CONTENTS. 



12 



8 8. Arsenic in 

$4. Antimony Ml 

... 

OHAFTSB w 

IllVAIIM N. S M I i \1>. 

148 

§2. Sulphur 

{ 8. Selenium 

M- Tellurium 180 

CHAPTEfi XVI. 

Vil" VDKIVAl.r.NT N.-N-MI T\\L6. 

181 

l'.'l 

$ 8. - 

Dtvwoa ii.— MF.TMs 
LPTEB xvii. 

!• 1. -Til!: M.K M.I MKTAL6. 

$ 1. Lithium 

§2. Sodium .211 



Rubidium ami Cerium 



tldum 



(II \I TEB xviii 

GROUP 1 — I I:IK M.K \ I.I M IM'.TIN 






% 1. Beryllium 
| J. M. ;_'?.- iwm 

f 4. Cadmium 



OB LPT] l: Xl\. 

-it m omorp. 









* 1. Thallium 
f2. Lead 



( II A! | 
I 



ftM 

H7 



X 



CONTENTS. 



CHAPTEE XXI. 

GROUP 5.— COPPER GROUP. PAGE 

§1. Copper 241 

§2. Mercury 243 

§3. Silver 245 

CHAPTEE XXII. 

GROUP 6.— CERIUM GROUP. GROUP 7. — ALUMINUM GROUP. 

§ 1 . Aluminum 253 

§ 2. Indium 259 

§3. Gallium 260 

CHAPTEE XXIII. 

GROUP 8. — IRON GROUP. 

§ 1. Manganese 261 

§ 2. Iron 262 

§ 3. Cobalt 273 

§4. Nickel 274 

CHAPTEE XXIV. 

Group 9 —Chromium Group : Chromium, Molybdenum, Tungsten, 

Uranium 275 

CHAPTEE XXY. 
Group 10. — Tin Group : Tin, Titanium, Zirconium, Thorium, Ger- 
manium 278 

CHAPTEE XXVI 
Group 11 . — Bismuth Group : Bismuth, Vanadium, Niobium, Tan- 
talum 281 

CHAPTEE XXYII. 

GROUP 12.— gold group. 
§1. Gold 283 

§ 2. Platinum, Iridium, Osmium, Palladium, Ehodium, Kuthenium . 286 

DIVISION III. — THE CARBON COMPOUNDS. 

CHAPTEE XXVIII. 

THE METHANE DERIVATIVES, OR FATTY GROUP OF HYDROCARBONS. 

§1. The Paraffin Series 291 

§ 2. Other Series of the Fatty Group 300 

§ 3. derivatives of Hydrocarbons 301 



• !Mi i: wiv 

HENZKNK IM OR AROMATI. ... 

t • : : • '. 1 





OB - \\ 



MS 

MS 

860 

' rs 







THE 
CLASS-BOOK OF CHEMISTRY, 



tNTRODUOTION. 

1. What is meant by Science. — That vast and varied 
.v <>f things which surrounds and includes us is known 

as Xat Liffer from each other in prop- 

's, and are constantly undergoing changes. Th< 

their properties and actions, are called phenomena* of 
ire: thi i, animals, and clouds arc phenomena; 

SO arc the freight, color, and hardness of a stone, the 

burning of oil in a lamp, the Freezing of water, and the 

Occurrence of thunder and lightning. Phenomena do not 

appear by chance nor irregularly, but are always produced 

Elite causes, and alw on in a regular way. 

Wal M mns up hill; fire never fails to hum the 

is thrust into it ; a person who is attacked by 
ise must living in unhealthful conditio] 

phenomenon take- place with an unvarying uni- 
formity, which is calh'd a Law. The whole system <>f 
laws is known as the Order of Nat knowl- 

edge i l >rder of Nature. 

2. The Science of Physics. I idy, 
science u divided into parts, which are known by diff( 

names. Among the phenomena of nature tl. 

mges which take place without thechs 

of tie- things changed -thus, \n be melted, d 

jxaramem. 



2 INTRODUCTION. 

ized, or made into filings, but it still remains iron ; water 
may be turned into the solid called ice or the vapor called 
steam, but it is the same substance still — and there are 
properties which influence changes of this kind, such as 
weight, divisibility, porosity, color, hardness, etc. Knowl- 
edge of such phenomena and their laws forms the divis- 
ion of science called Physics. 

3. The Science of Chemistry. — But matter may un- 
dergo changes by which its distinctive characters are 
altered. Thus, bright iron, when exposed to damp air, 
is converted into a brown rust. When vinegar and lime 
are brought together they combine, losing their prop- 
erties, and producing a new and different substance. 
When wood is heated, in the absence of air, it is changed 
to a black, brittle mass ; if heated in the presence of air, 
it is changed to invisible gases and ashes. Different 
things behave differently when exposed to damp air, when 
brought together, or when heated, etc., according to their 
peculiar properties. Knowledge of such changes and of 
the properties and conditions which influence them forms 
the science of Cliemistry. 

4. Chemical Physics. — So closely are the forces of na- 
ture connected, that the disturbance of any one of them is 
sure to involve a disturbance of others. Physical forces 
and conditions have such a powerful influence over chemi- 
cal actions that some knowledge of them is indispensable 
to the student of chemistry. Several substances are de- 
composed with an explosion by merely touching them with 
a feather. Wood takes fire only when strongly heated; 
chlorine and hydrogen gases combine with explosion in 
direct sunlight, but not in darkness. INTo chemical change 
can occur without being accompanied by some kind of 
physical change. Accordingly, under the title " Chemical 
Physics," we first treat briefly of those physical agencies 
which are most intimately connected with the subject of 
chemistry. 



PART I. 

OHEMIOAL PHYSIOS. 



CHAPTBB I. 

MATTKK AN1> IT- KBA8URBMBNT. 

5. Matter. — Whatever occupies space — whatever wc 
can see, feel, taste, or smell, Lb termed matter. All things 
in natoi I of matter. Any separate portion 
of matter is called a body, and different kinds of matter 
are known as s u bstances. Matter exists in three stab 

>U& Most suhstanees can he Dott- 
ing or COOling them from one of these states 

ither of the others. 

6. Volume, Mass, and Density. — The quantity of space 
which a body occupies is called its volume, or bulk. A 

rving-knif e has a greater volume than a needle, and a 
tnh of volume than a tumblerful. When 

we say that one thing has more volume or hulk than an- 
other, we mean thai one is larger than the other. 
• quantity of matter in any body is termed i 

olume, though generally the bo 
, tie- ii is ii occupies. Bui a 

.n be compressed into ■ small 

. e without takii of it- ma-. Thus, a lump 

w can be squeezed down to a hard snow-ball, which 
will be much -mailer thai imp was, bul will have 

of .-now in it. In other WO 
ISB, whil 



CHEMICAL PHYSICS. 



In the snow-ball the particles of snow are crowded to- 
gether closer than they were in the lump — there are more 
of them in an equal space. We express this difference by- 
saying that the snow-ball is denser than the lump of 
loose snow. The density of a body means the closeness 
with which its particles are packed together. Density is 
increased by compression, and diminished by expansion. 

7. Measurement of Matter. — In performing chemical 
operations it is constantly necessary to compare the vol- 
ume, mass, and density of different bodies ; and, in order 
that we may make accurate comparisons, we must use the 
process called measurement. The mass of a body can not 
be measured directly with convenience, hence its weight, 
which is always proportional to its mass, is measured in- 
stead. 

8. Weight. — All bodies on the earth are drawn to- 
ward its center by the force called gravity. This attrac- 
tion makes each body exert a pressure upon whatever is 
beneath it, called its weight. This pressure is greater or 
less in exact proportion to the mass of the body. If one 
body has twice as much mass, that is contains twice as 
much matter as another, its weight will be twice as great. 
Weighing consists in ascertaining the force with which 
any given body is pulled toward the earth, by comparing 

the body with other masses 
of matter already weighed, 
and marked according to 
some fixed standard. But 
weight is subject to one law 
which does not affect mass. 
If a body is removed far- 
ther from the center of the 
earth, its weight diminishes, 
while its mass, of course, 
remains the same. 

9. The Balance. — The instruments employed by chem- 




STANDARD WEIGHTS AND UEASURES, 



in weighing are balances. The chemical balance 
. l ), used tor analysis, consists of an Inflexible barj 

delicately poised at a point exactly midway 
reen its extremities, from which the Bcale- 
- are suspended. Its beam rests upon a 

fine edge of hardened steel, which is supported 

by a flat plate of polished agate. 

10. Measurement of Volume. — The vol- 
ume of a body, that is the Bpace it occupies, 

.red by comparing it with a fixed 
taken aa a unit. This unit 
died a measure of volume or capacity. 

11. Standard Weights and Measures. — 
For ordinary purposes the pound avoirdupois 

r unit of weight, and the gallon and cubic 
inch are our units of capacity ; hut in making 

litic investigations the metric system, 

called also the decimal or French system, of 

'its and measures is now almost univer- 
employed. 

12. Metric Weights and Measures. — The 
basis of the metric Bystem of measures is the 

•. a length about three inches greater 

than a yard. To the decimal divisions of this 

In names composed of the word meter 

and a prefix formed from a Latin numeral 

1 the decimal multiples 

of tl length are similarly named by 

• •k numerals. Tim- : one tenth 

of ifl called a decimeter j one hun- 

dredth, a • •••iitine mdth, a millimeter. Ten 

p, one hundred a hectometer, 

thousand a kil<> 

11* ■ • . Or the Mi /•. i- the unit n. 

♦ •rally used a- rd <>f volume, hut the oubifl 

often employed. To com] 



■ KM milli- 
DMfe 



6 



CHEMICAL PHYSICS. 



<^=} 



c.c. 



measures with one more familiar, it may be remembered 

that a liter is a little more than a quart liquid measure. 
The metric system of weights is based upon the metric 

measures. The standard unit of the scale is the weight 
of one cubic centimeter of pure water at 
the temperature of greatest density, 4°C. 
(39*2° Fahr.), and is called a gram. The 
subdivisions and multiples of this unit 
are distinguished by the Latin and Greek 
prefixes already mentioned. The gram is 
equal to about 15^- grains ; one thousand 
grams are called a kilogram, equal to 
about 2£ pounds avoirdupois. Tables of 
equivalence of French and English weights 
and measures are given in the Appendix. 
13. Calculation of Density. — The den- 
sity always depending on the volume and 
the mass of a body, is calculated from 
these instead of being measured directly. 
The calculation consists in dividing the 
weight (which represents the mass) by the 
volume. Thus, to get the density of 
wrought-iron, we find its weight is, say, 
2,886 grams, and its volume is 370 cubic 

centimeters. Dividing 2,886 by 370 will give the density, 

which is 7 # 8 grams to a cubic centimeter 



Fig. 3.— A five Cubic- 
centimeter Meas- 
uring-Glass. 



CHAPTER II. 

SPECIFIC GRAVITY. 



14. Specific Weight or Gravity. — Equal volumes of 
different substances differ in weight, as shown in the fol- 
lowing table. Thus, 1,000 cubic centimeters 



SPECIFIC (iRAVm 7 

.118. 

Off I 

•• iii * 

4 ' ill •' 809'fi 

l.' 

" iron "....... 

" platinum 4i Bl,fl 

Platinum, which, next to osmium, is the heavies! substance 

known, ifl thus nearly a quarter of a million times heavier 
than an equal bulk of hydrogen, the lightest of known 

If we determine not the absolute weight of 

a body, hut its weighl compared with an equal hulk of 
stance, we obtain its relative weight, or ( 

ritir gravity. Water, irhich is found everywhere upon the 
v purified by distillation, is taken a.s the 

unit of comparison f or solids and liquids. As variations 

Of ' 'lire alter the hulk of bodies, sp. gr. is taken 

!'.) or at Lfi I V.). 

In the metric system the weight of one cubic centimeter 

0. [ual to one gram. The freight of 

iccentin t any substance at that temperature, 

grams, is therefore identical with its specific 

:ty. 

• determining the specific gravities of sul 
employed, dif- 
fering according to whether the >\\\)- 
ration is a solid, 

a liquid. gas ; whether it is 

r than water, or dis- 

it. 

15. Solids heavier than Water. 

— Any when im- 

ied in i iplacei s volume 

exa' n hulk. Kill i 

a vessel with n and 

to it a • sulphur which 

[uantitj of water will then h.l<>w, 




i 



8 CHEMICAL PHYSICS. 

equal in bulk to the sulphur. Weigh the water that has 
run over. If the sulphur weighed two ounces, the water 
will weigh an ounce. That is, the sulphur weighs twice 
as much as an equal volume of water ; its specific gravity 
is therefore 2. 

A solid substance immersed in water loses a portion 
of its own weight, just equal to that of the volume of 
water displaced. Hence, the best plan is to suspend the 
solid to the scale-pan of a balance by a fine thread or hair, 
and then counterpoise it, or get its weight in the air. 
Now immerse the suspended body in a vessel of distilled 
water (Fig. 5), and as it weighs less, remove weights enough 

from the opposite scale- 
pan to restore the lost 
equipoise. Divide the orig- 
inal weight in air by the 
loss in water, and the quo- 
tient is the specific gravity 
of the substance. For in- 
stance, a piece of lead 
/r-J weighs in air 820 grams, 

/ — - \ and in water 71 grams less. 

a»iltlltltiilillilllli»*ittltltlUttIlit»tlitltUtlUtllUlllllll»lltlllUillil»lllillltUT¥lY¥TTmFfTll . . ° . . . 

w ^ The weight in air divid- 

Fig. 5.— Weighing a Substance in Water. r* 

ed by the loss in water 
gives 11-5 as the specific gravity of the lead. (820 -~ 71 
= 11-5.) 

16. Solids lighter than Water. — When the body to be 
examined is lighter than water, it is first weighed and 
afterward attached to a piece of metal heavy enough to 
sink it, and suspended from the balance. The weight of 
a bulk of water equal to that of the piece of metal and 
light body together is thus found. The piece of metal 
alone is then weighed in water, and the difference between 
the weights of the two bulks of water displaced gives the 
weight of water displaced by the light body. Thus, sup- 
pose we have a piece of wood weighing 40 grams and a 




SPECIFIC GRAVITY. o, 

pieoe of metal weighing 18 grams, making them weigh to- 
iler ss irrams. In water they weigh together 80 grams, 
; this subtracted from ss -rams gives 68 grama as their 

weight in water. The metal weighs 40 irrams in 

water, hence its Loss6f weight is 8 -"ram-; subtracting this 
bom 68 grama Leaves ♦ '• ,l grama as the loss of weight of the 
d. Dividing 10 by 60 givea '666 as the specific grav- 
ity of the wood. 

17. Powdered Solids. — The specific gravity of any sub- 
stance in powder — as, for instance, a soil — is obtained as 
foil tunterpoise a hundred-gram bottle ami weigh 

into it 16 grama of soil to be tested. Fill with water and 
Bgain; water and soil give, say, lOiHi irrams, L5 of 

them arc soil and 91*6 water; consequently, 5*1 grama of 

water have been displaced by L5 grams of soil. The cal- 
culation is then eaay, 5*4 : I :: L6 : 'Mil sp. gr. of the 
soil. In practioe a precaution is to be observed. The 

soil contains air among its particle-, which would gives 
WTo It To prevent this, till the bottle only half 

full of water at first, and shake it well with the soil ; the 

air escapes, and the bottle may then be filled up. 

18. Soluble Solids. — When the substance to be exam- 
i is soluble in water its specific gravity is determined 

by substituting for the water some other liquid that <! 

it. and the exact specific gravity of which is 
known. The bulk of water corresponding to the bulk of 
I liquid displaced may be found by simple 
pr« The liquids most generally used in these de- 

re alcohol and oil of turpentine If we put 
• f a solid into a weighed bottle <»f turpentine 

and find that i. is of the liquid are displaced, then 

-f- L25 - l ••*'. L r i\ii .. the solid with ref- 

to turpentine. Thi of turpentine ref.-rred 

>, and 1*6 X 790 = L*264* which ii the 
gr. of the solid referred • 

19. Liquids, i the specific gravity of 



10 CHEMICAL PHYSICS. 

liquids, procure a small bottle and make a fine mark with 
a file and ink upon its neck. Counterpoise it in the bal- 
ance. Fill to the mark with distilled water at 15° C. and 
weigh it. Empty, dry, and fill again with the liquid, the 
specific gravity of which is required. Its weight, divided 
by that of the water, gives the desired result. Suppose the 
bottle holds a hundred grams of pure water, it will be found 
to hold 184*5 grams of sulphuric acid, which therefore 
has a sp. gr. of 1-845. For 100 : 1 :: 184-5 : 1-845. It 
will hold 1,350 grams of mercury, the sp. gr. of which is 
hence 13*5 ; or 103 grams of milk sp. gr. 1*03. In practice 
it is usual to employ a bottle (Fig. 6), hold- 
ing exactly 100 or 1,000 grams of distilled 
water at 15°, which shows the result at 
once without calculation. 

20. Oases. — The specific gravity of 
gases is obtained in several ways. One 
method is as follows : A flask or globe 
suspended from the arm of a balance is 
Fig. 6. — specific weighed when emptied of air, and again 

Gravity Bottle. _ to • _ . , . m . . , 

when filled with air. This gives the 
weight of air, which is taken as unity. Other gases are 
then substituted for the air, and their comparative weights 
ascertained. The results are sometimes reduced to a scale 
with hydrogen as the unit. Gases are subject to varia- 
tions of density, not only by alternations of temperature, 
but by changes of atmospheric pressure ; these weights are 
therefore taken at the barometric pressure of 760 milli- 
meters, and the temperature of 0° C. If a flask when 
filled with air weighs 12 grams more than when empty, 
and when filled with a certain gas weighs 12*5 grams 
more than when empty, then 12*5 divided by 12 gives the 
sp. gr. of the gas, which is 1*04. 

21. Hydrometer. — Take a light, slender-necked bot- 
tle, loaded with shot, and float it in pure rain-water; 
it will sink to a certain depth, which may be accurately 




IMPORTANCE OF SPECIFIC GRAVITY, 



11 



marked upon the glass. If now placed in brine 

milk, the mark will stand above the surface; the V« 
not sinking BO deeply as before, because the liquids 
heavier. Place it in alcohol, and the mark will dis- 
appear below the surface; it sinks deeper than at first, 
ause the liquid is lighter than water. Instruments 

arranged on this principle, and called ////- 

drtmeters, are used to measure the specific 

of fluids. They usually consist 
a glass stem (Fig. 1), terminating in a 

bulb below, loaded with shot or mercury, 

and floating in a narrow glass vessel, con- 
taining the liquid to be tested. Scales 

fixed within the stem, zero being the 
point at which the instrument sinks in 
distilled water at 15 C 0. In lighter liquids 

sinks deeper, and the Bcale is read up- 

1 from zero. In heavier liquids it 

floai r, and the scale is read down- 

i from zero. These scales are arbitra- 
ry and different in the various instruments. 
Tal ompany them, bo that we see at a glance the 

gr. which corresponds to any number upon the scale. 
The hydrometer is no4 bo accurate as the sp. gr. bottle, 
but much more Convenient Instruments of this kind 
are much used by manufacturers and dealers to determine 
the gravity or tfa of liquors, sirups, oils, 

22. Importance of Specific Gravity. Specific gravity 
is anions t ; mt of the physical proper! 

of ful means of identifying them. 

Tin .1. iron pyrii \amph\ i> i 

•tly lik«- gold, and is frequently mistaken for it B 

it i died by the di£ 

. •. ity, an equal bulk of gold b. 

than p. >ld l- del / H 




Pig 



12 CHEMICAL PHYSICS. 

with a cheaper metal, taking the specific gravity promptly 
detects the fraud. The proportion of alcohol in spiritu- 
ous mixtures, the richness of milk, the strength of various 
solutions employed in the arts, and the identity and purity 
of many substances, are determined with more or less 
accuracy by the same means. 



CHAPTEE III. 

MOLECULAK ACTION. 

§ 1. Minute Constitution of Matter. 

23. The Structure of Matter. Porosity. — From the 
properties which belong to masses of matter, we now pass 
to the study of the properties which depend upon its 
minute structure, or upon the manner in which it is 
believed to be made up. If we place a little water upon 
chalk or cloth, it disappears ; in a certain sense it pene- 
trates the substance, but it only passes into vacant places 
termed pores. Not only loosely composed substances, as 
soil and flesh, but wood, stones, and even dense metals, 
have a similar porous texture. Liquid mercury passes 
through solid oak, and water has been forced through the 
pores of gold. Matter is, therefore, held to be universally 
porous. 

24. Motions of the Particles of Matter. — If a closed 
India-rubber bag, filled with air, is squeezed, it will be 
compressed into less bulk — that is, the particles of air will 
be forced nearer together. If alcohol and water are mixed, 
the mixture occupies a smaller space than did the sepa- 
rate liquids ; their particles have, therefore, come closer to 
each other. If iron is hammered, it will be driven into 
less compass, the metallic particles being forced nearer 



U0L1CULE8, 13 

ether. Heal imparted to any bodies, whether solid, 
Liquid, or gaseous, will oanae them to enlarge, thai is will 
make the particles reoede from each other; and as the 
heal i> withdrawn, the particles again conic together. 

25. Molecules. — It is concluded from such t, tiese 
that matter 001 very minute particles, which never 

LOh each other, but are BUTTOUnded by enipt\ spaces, in 

which they are free tO move. These particles are termed 

hcules, a wonl meaning a small mass. Although too 
small to be Been, to the physicist molecules are not mi- 
liary, bin are actual things with weights ami ?olun 
I which «lo n..t change in the physical transformations 
of matter. Molecules play a prominent part in modern 
physical theory. Their chemical aspect will be considered 
in the chapter on "Theoretical Chemistry." 

26. Divisibility of Matter. — Hatter may be divided 
almost indefinitely. Gold has been drawn out as a coating 

upon Bilver wire until the 492-thonaand-millionth part of 
is still visible, with its proper color and luster. 

It has been estimated that, in a drop of the blood of the 

musk-deer, such as would remain suspended upon the 

Mt of a needle, there arc one hundred and twenty 

million bulcs. Hut these examples of the «Ii\isi- 

bility of matter bring as only to the threshold of a world 

wonders. Microscopic study has shown US a realm of 
life peopled with animate beingB, which arc born. gTOW, 

reproduce their kind, and die; and vet N minute that 
many millions of them heaped together would not exceed 

I L r rain of sand. 

27. Molecular Motions. - Molecular im upposed 
to have three kinds of motion. In BOlldfl the] maintain 

placet, but vibrate at varying rates. In 
liquids the molecules are less clowly bound to 

i each other >n rapidl i\c rise to 

tic liquid diffusion. When the riolence of these 
\ is increased b the mo|, 



14 



CHEMICAL PHYSICS. 



yond cohesive restraint, and assume the condition of gas. 
No longer influenced by mutual attractions, they are now 
supposed to move with far greater energy, flying about in 
all directions, in extremely short, straight paths, striking 
and rebounding from each other, and giving rise to an 
expansive pressure, known as gaseous tension. This is 
the molecular explanation of the phenomena presented by 
the three states of matter. 

§ 2. Cohesion and Adhesion. 

28. Cohesion. — Though the molecules of a solid are 
separated, yet it does not crumble to pieces. They are 
held together by a force which reaches across the spaces 
between them and binds them in a fixed relation. This 
force, when acting between particles of the same kind, is 
termed cohesion. The form, solidity, hardness, elasticity, 
brittleness, malleability, and ductility of solids, are the re- 
sult of various modifications of cohesive force. There is 
also a mutual but less strong attraction among the parti- 
cles of liquids. In a drop of liquid,. cohesion attracts the 
particles into a rounded figure against the influence of 
their weight, which would spread them out. 

29. Adhesion. — A similar force acting between parti- 
cles of different kinds of matter is called adhesion. The 





Fig. 8.— Glass Rod in Water. 



Fig. 9. — Attraction of Glass and Mercury. 



sticking of chalk to a blackboard, of mortar to bricks, 
and of water to a glass rod, are examples. The adhesion 
of a liquid and a solid is often strong enough to raise the 



CAPILLARY A 1 IK LCTION. 



i;> 



particles of the former which touch the solid above the 
level of the liquid Iftramples of this action are shown in 

J i B and \K 

30. Capillary Attraction. - I f small ejass tulu»s open at 
both ends (Pig. L0) be dipped in water, the liquid imme- 
diately rises in them to a height which increases in pro- 
portion to the smallness of the hoivs. From the circnni- 

tnoe that this effect is beet produced by tubes with rery 

tine bores, the attraction that causes these phenomena is 

called capillary (from capillus, a hair). The same thing 
may also be beautifully exhibited by placing two plate of 

1 1 ) upon their edges in a dish of colored water. 




n._. ... .Mill? 




-Capillary Tube*. 



Fie;, i ' Liquid bet* 



touching each other at one (nd and slightly separated at 
the other. The influence <>f the gradually approaching 

e> of the plates in attracting the liquid upward i> Been 

in the COUne <-f the curve. 

31. Adhesion of Gases to Liquids. — When a liquid is 
red from one vessel to another, as in filling a glass 

with water, air adheres to th«- descending stream, u car- 
! downward, and maybe seen as bubbles rising through 

ter in the glass, while a portion of it remains OOin- 

bined with the water. If the water it heated, adhesion 
iiminisl ir expands, hence the read 

• f driving L r as from solution in by l>»>iliiiL r . 

32 Adhesion of Oases to Solids. It iron til 

the surface of water, they Boat, thou 
inc This is becaua of 



16 



CHEMICAL PHYSICS. 



the adhesion and condensation of a layer of air upon the 
surfaces of the filings, which prevents the water from wet- 
ting them. The condensed air forms a little envelope 
around the particle of iron, and thus displaces a large 
volume of the liquid in comparison with that of the solid. 
Insects skim over the surface of water because the air 
adhering to their feet forms capillary cavities which pre- 
vents them from becoming wet. 

§ 3. Diffusion. 

33. Diffusion. — Whenever the cohesive force between 
the molecules of any body is exceeded by the adhesive 
force between its molecules and those of another body, 
the cohesion of one or both bodies is overcome, their mole- 
cules separate and intermix. The bodies in this case are 
said to be dissolved in or diffused through one another. 
The process is called diffusion. This term is generally 
limited to those cases where gases mix 
with gases and liquids with liquids. 

34. Diffusion of Gases. — When differ- 
ent gases are brought together they readi- 
ly mingle because their molecules have no 
cohesive attraction. Bare gases diffuse 
more freely than denser ones ; but the 
action always takes place even in opposi- 
tion to their specific gravities. Thus, if 
two jars are connected by a narrow tube 
(Fig. 12) and the lower filled with carbon 
dioxide, the upper containing hydrogen, 
diffusion takes place through the narrow 
passage. The light hydrogen descends, 
and the carbon dioxide, though twenty 
Fig. 12. — Diffusion times heavier, rises, and they become 

of Gases. . J 

equally mingled in both jars. Our at- 
mosphere owes its stability to this principle, its constitu- 
ents being perfectly intermingled. The baneful products 



cfH = 





DIFFUSION. 17 

of respiration, ion, and decay, instead of aooumii- 

lating, are incessantly being dispersed in the atmospheric 

35. Diffusion through Porous Partitions. — Diffusion 
takes place also through the pores of dry plaster of Paris, 
india-rubber, and other porons substances. A sheet <>f In- 
dia-rubber tied tightly over the top of a pride-mouthed 
jar containing hydrogen is soon 
pressed inward, oven to bursting. 
If the jar is tilled with air and 
placed in an atmosphere of hydro- 

, the swelling and bursting 

outward (Fig. L3). If 

the membrane is moist, the result 

effected by the different 

solubilities of the eases in the ^ 

throiiL'h Membr 
water or other lnjiml which wets 

it. Though the diffusive power of carbon dioxide is small 

with that of sir, yet it easily passes into the 

latter through wet bladder. This process appears to be 

Night into play in atmospheric respiration. There 
air on one side of the moist lung-membrane and blood on 
th< is transmitted from the air to the 

urbon dioxide from the blood to the air. 

36. Diffusion of Liquids. — That the molecules of liquids 
may be seen in the formation and persistence of 

drops; but ..force in liquids is never sufficient to 

unit masses. The adhesive attraction of the mole- 

cules of different liquids, on the other hand, is in many 
cases ve ; lerable. Diffusion of liquids through each 

_rh not as gem ml ;t~ tl. i-es, i^ \ 

nt. Thus, if a tall g filled * uli water oolored 

with ink, i .hoi (which is lighter than wwi 

pound carefully on the top so ;i- not to mil tie- | 
li<l .. tine- be found mingled. 

• liquids diffuse with rery unequal relocities. Diffusion 



18 



CHEMICAL PHYSICS. 



is generally found to take place more rapidly at high than 
at low temperatures. 

37. Crystalloids and Colloids. — Diffusion is particular- 
ly rapid with solutions of substances which will crystal- 
lize, like sugar, salt, etc., and slowest with substances 
which do not crystallize, like gelatine, gum, etc., and 
which are capable of forming jellies. The former have, 
accordingly, been called crystalloids, the latter colloids. 
Crystalloid bodies form solutions which flow easily, while 
the solutions of colloids are sirupy. 

38. Diffusion of Liquids through Porous Partitions. — 
When a piece of moistened bladder is tied tightly over 
the end of a tube placed in a vessel of water, and then 

filled with alcohol up to the level of 
the outer liquid, the fluid in the tube 
will shortly begin to ascend, and may 
rise to a considerable height (Fig. 
14). The water passes through the 
membrane and mixes with the alco- 
hol, while at the same time a slight 
current of alcohol flows the other 
way and commingles with the water. 
When different liquids are separated 
by a membrane in this manner, that one is transmitted 
fastest which wets the barrier most perfectly. This ac- 
tion is due partly to their adhesive attractions for each 
other, and partly to the difference of their adhesive attrac- 
tions for the membrane or diaphragm, the pores of which 
act as short capillary tubes. 

39. Diffusion of Solids in Liquids. Solution. — The 
diffusion of the particles of a solid among those of a liquid 
is termed solution. The solid becomes finely divided, 
and disappears, mixing uniformly with the liquid, which 
remains transparent. The solid is then said to have been 
dissolved and the liquid employed is called the solvent. 
A liquid which dissolves one substance may not dissolve 




Fig. 14.- 



-Osmose of Liq- 
uids. 



80LUTI0N, L9 

another, while substances insoluble in one liquid are d 
solved by others. 

40. Diffusion of Gases in Liquids. — Qasefl are taken tip 
or dissolved bj liquids, and water, the most common 
liquid, shows this property in a marked degree. The 
absorptive power of liquids varies for differenl gaa 

cold increases it, heat diminishes it. Pressure 
<ften employed to induce absorption, as, for example, 
when water is charged with carhou dioxide to form the 
drink called soda-water. 

41. Conditions favorable to Solution. — Whatever weak- 

en favors solution. Thus, by powdering a suh- 
. its Cohesion ifl partly destroyed and the Mirfacc 

increased; solution is consequently promoted. Heat, in 
moc . contributes powerfully to solution, its effi 

being to weaken cohesion by increasing the distance 
d the particles of the solid; yet there are several 
marked tions. Water just above the freezing-point 

as much lime as at the boiling-point, while 

the solubility of common salt seems hardly affected by 
perature. Some substances increase in solubility regu- 
larly as the temperature increases ; in many case- the solu- 
bility increases faster than the temperature, ami in others 
\ with the increasing heat to a certain point, and 
thru falls while the temperature continues to ascend. 

42. Saturation. — A liquid is said to be saturated when 
it has taken up all of a substance that it can dissolve at a 

r IS the common BOlvent, and 

so general is its use that, in speaking simply «>f the solu- 
bility of a body, water is always meant. 

43. Separation of Solids from Solution. If theadht 

renl and the 

on reunites the mo 
of the solid into visible particles. T be 

s — as, when tie moved 

another liquid which will i 



20 CHEMICAL PHYSICS. 

dissolve the solid is mixed with the solution. Thus, if 
water is mixed with a solution of camphor in alcohol, the 
camphor separates as a white cloud, at first rendering the 
liquid turbid, but, after some time, settling on the bottom 
of the vessel. When a solution is evaporated, the solid is 
deposited either during the process, or remains at its 
close. The former is generally the case with crystalloid, 
the latter with colloid bodies. The instantaneous separa- 
tion of a solid from a clear liquid is termed precipitation, 
and the deposit formed, a precipitate. 

44. Diffusion of Gases in Solids. Occlusion. — The fact 
that gases adhere to solids has already been noticed. 
Under some conditions, certain solids absorb large quanti- 
ties of gases, which may be said to be diffused through 
the mass of the solid. Thus, charcoal and the metals 
iron, platinum, and palladium, have the power of taking up 
various gases ; the last-named metal is said to be capable 
of uniting in this way, at ordinary temperatures, with 
several hundred times its own bulk of hydrogen gas. 
This diffusion of gases in solids is termed occlusion. 

§ 4. Crystallization. 

45. Crystallizable and Amorphous Substances. — Under 
various conditions, and particularly when bodies pass 

from the liquid or gaseous to the solid state, 
their molecules tend to arrange themselves 
in regular geometrical forms termed crystals, 
of which Fig. 15 may be taken as an exam- 
ple. The substances in which this tendency 
exists are said to be crystallizable, and the 
process of their formation is called crystal- 
lization. Many substances, however, do not 

Fig. 15.— Form crystallize. These are said to be amorphous, 

crystai? uartz this molecular condition being called amor- 

pJiism. Water, salt, sugar, are examples of 

crystallizable, gum and glass of amorphous substances. 




STALLIZATION 



81 



46. Crystals in Nature. Nature terms with crystals. 
They fall in the form of snow from the clouds; and io 

tls, only bo blended that ire can not readily 
;i>h the 53 teaches thai the materials of 

the formerly in ■ melte ml that, in the 

lification, an opportunity on the grand- 
scale for the formation of crystals occurred. Quarl 
tmmon rock which form-.; rystala It U gen- 

By found as a white or tinted vein in other rocks. 1 

L5 ahowB the typical form of quarts crystals, bul khey arc 

lv BO crowded 
I be very 
ind one 
end IS always fan- 
in an nn< 

:e com- 
mon ap « of 
quart fa in na- 
ture, rocky 
beds haw their i 
stitm rtalliiftd t 
and are known as 

stalline rocks. Crystals may be produced in fan 

i, by the slow cooling of melted bod- 
lensation <>f gases, or even 

* of the molecules of So! 

47. Crystals from Solution. It bas already been stated 
.' the solvent power of liquids for any solid ! 

greater at high than at Ion atures. 

ntion of ich 

rice — as, for • .alum in water i- silo 

cool, a portion «>f tl !rom the solution in 

form The liquid which remains after 

their f ■■■ - ceased is railed th»- If 

sev. stances are (lis.- n the solu- 




of tyuurti < 



22 CHEMICAL PHYSICS. 

tion is cooled or evaporated, the one least readily soluble 
will crystallize out first, and may be separated from the 
others by pouring off the mother-liquor. In this way salt 
is obtained from sea- water, which contains also gypsum 
and other substances. 

48. Crystals by Fusion. — Nearly all bodies when cooled 
after melting solidify in the crystalline form. The spaces 
left between the crystals which first form are completely 
filled by the portions which solidify afterward, so that 
fracture reveals, instead of distinct crystals, only a con- 
fused crystalline structure, as may be seen in broken cast- 
iron and zinc. Common sheet-tin is 
beautifully crystallized, though it is not 
apparent. If with weak acid we wash 
off the thin surface-film of metal, which 
had cooled too fast to crystallize distinct- 
ly, the structure will be revealed ; it has 
a beautiful feathery appearance. To ob- 

FlG * crysta?s phur tain good crystals by fusion, the excess of 
liquid must be removed from around 
those which are first formed. If a quantity of sulphur is 
melted, and then allowed to cool till a crust appears upon 
the surface, crystals will be formed within, which may be 
seen either by breaking the vessel (Fig. 17), or by piercing 
the crust and draining off the interior liquid. 

49. Crystals by Sublimation. — Solid substances vapor- 
ized {sublimed) may be condensed in the crystalline form, 
as iodine, sulphur, arsenic. Camphor thus vaporizes and 
condenses in brilliant crystals upon the sides of apothe- 
caries' jars by the rise and fall of common temperatures. 

50. Crystallization in the Solid State. — The strong 
tendency of molecules to assume crystalline shape is mani- 
fested even in solids. Thus barley-candy, at first trans- 
parent and amorphous, after some time becomes crystal- 
line and opaque. Glass, by a long-continued low heat, 
though it does not melt, becomes also opaque and crystal- 




PHENOMENA OP GRYSTALUZATIOti 

line ( RSaum *U tin). Brass and diver, when I 

cast. >ugh and uncrystalline, but, when repeatedly 

heated and cooled, they become brittle, and Bhow traces of 
. stallisatioiL Metals, by hammering, lose their •Inu- 
tility and tenacity, and, by tin- rearrangement of their 
particL dline and brittle. Coppersmiths, 

whm hammering their frequently anneal them, to 

rent their flying top thai is, they heat them, and 

thru allow them to slowiv COOL Thus also hells, long 

rang, change their tone; cannon, after frequeni Bring, 
lose their strength, and are rejected ; and bo the perpetual 

jar and vibration <>f railroad-axles and the shafts of ma- 
chinery gradually change the tough, fibrous wrought-iron 
into t h- be, weakening it and increasing its 

liability t<> break. 

51. Phenomena attending Crystallization. — The change 

mdition is usually attended by change 
of balk. Water, in fn expands with greal power; 

elling to eleven cubic centi- 
: and -tlie for ted by the particles in 

is so enormo burst the Btronj 

iroi l 'ii is usually attended with pro- 

duction of heat in proportion to the rapidity of the action. 
:it has also occasionally been - ompany the 

Muddy and impure solutions often yield the 
lar.L' i the pr ibstanoes which do 

iay thus modify the form w hloh 
ital assumes. Wh. • roken, th< 

pair it ; it emitiniies tu in 

direction, b re upon the En 

inline of tl 
reston-d in a few ho 

52. Conditions of Growth. Jarring maj 10 disturb the 

Idom p« - 
generally irregular, disguised, and 



24 



CHEMICAL PHYSICS. 



alum-crystals, for example, are regular octahedrons (Fig. 
18) or cubes, bat Fig. 19 shows how they appear in the 





Fig. 18.— Octahedral Crystal. Fig. 19.— Masses of Imperfect Alum-Crystals. 



large vat of the manufacturer. Sometimes the attractions 
are so balanced that a jar is needed to start the action. In 
a perfectly still atmosphere, water may be cooled eight or 
ten degrees below the freezing-point without congealing, 
but vibration of the vessel produces a sudden crystalliza- 
tion of part of the liquid into ice. Any solid body put 
into the liquid may, by adhesion, destroy the equilibrium 
and begin the play of the crystallizing forces. Thus, 
threads are stretched across vessels containing solutions of 
sugar, and form a nucleus around which rock-candy is 
crystallized. 

53. Forms of Crystals. — The force of cohesion acts 
symmetrically. Leaving disturbing influences out of 
view, all liquids tend to assume the spherical shape of 
drops. We might, therefore, anticipate that, in returning 
to the solid state, their molecules would still group them- 
selves round centers into spheres. But, although some- 
thing of this kind may take place with amorphous bodies, 
the forms produced in the solidification of crystallizable 
substances are angular, and bounded by plane surfaces 
symmetrically arranged. Single crystals often present a 
large number of faces, but the position of all these bears 
a fixed mathematical relation to imaginary lines, three or 



PORMS OF CRYSTALS. 



as 



four in Dumber, passing through the center of the crystal, 
I called its axes. The simplest Bhapes which can be 

'lie axes are called primary forms. 

54. Systems of Crystallization.— All known crystalline 
form- have been classified and arranged in a Dumber of 

ips termed s \ Uallization* There are Ai 

of theei as, and the forms belonging to each differ 

from the forms belonging to the other Bystems, either in 








Pio -j: D 





Flo. flL— Trimetrir «»r < Irthorbombk 



' 








the Dumber <>r the relatr h of the 

_ r le- whi«-)i the axei ! their h on in 

r of the crystal Tl 

leen in : 



26 



CHEMICAL PHYSICS. 



55. Derivation of Form. — The cube (Fig. 26) may be 
taken to illustrate change of figure, and this is chiefly ef- 
fected by replacing edges and angles by planes. The cube 
has twelve edges and eight solid angles. If plane surfaces 
are substituted for the edges, we get the secondary form 
(Fig. 27). If we replace the solid angles by planes, we 
have the form Fig. 28. If both these replacements occur 
together, the more complex form (Fig. 29) results. If the 
edges of the cube are replaced until all traces of the origi- 





Fig. 26 




Fig. 27. Fig. 28. 































Fig. 29. 



Fig. 30. 



Fig. 31. 




Figs. 26 to 31.— Transformations of the Cube. 



nal planes disappear (Fig. 30), the rhombic dodecahedron 
is formed ; and, if the solid angles are replaced by 
planes to the same extent, we get the regular octahedron. 
(Fig. 31.) 

We have said that the secondary or derived forms of 
crystals are almost innumerable. Six hundred modifica- 
tions of the six-sided prism have been enumerated by Dr. 
Scoresby among snow-flakes ; while M. Bournon, in a two- 
volume treatise, has delineated eight hundred different 
forms of the mineral calcite (calcium carbonate). Hauy 
has described a single crystal which had one hundred and 
thirty-four faces. 



KXPAN8I0N BY HEAT. 07 

56. Isomorphism. When dihVrcnt suhstances take 

d theme tesame primary form or modifloatii 

it, they are said to Ij //>//<>//>, and the law whiob 

- their Identification is called isomorphism) bom 

< . equal, and , form. Thus gold, sil- 

. copper, alum, Bait, and nianv other bodies, all <t \slal- 

Bame forma of the isometric Bjstem. Such 

rfect identity is, however, only met with in forms of this 

item, [somorphous bodies, when crystallizing from 
mixed solutions, frequently remain diffused through one 

•ther in the Bolid Mate. Some substances cnMallize in 

•it forms, and are called dimorphous. Thus, 

Sulphur deposited from solution takes one form, and when 

from melting, another. Niter crystallizes in one 

quantities, and takes another shape in small 

quantities. Substances crystallising in three forms arc 



CHAPTEB IV. 

Hi: a I A Mi CHEMICAL CH I KG 

//. Thermometsrs. 

57. Heat exorti a very powerful influenoe over the 
states of matter, and mportanl for the prodm 

of chemical effed the chei en called the 

M Philosopher by Kirc" Tin 

Tom the Qreel thermos, bot, which 

58. Expansion of Solids Beat tendi to I the 
particles of matter farther apart, thus expanding or in- 
creasing thesiseof tht maw All ; uni- 
form constitutioi qually in all dip when 

heated, whih 




28 CHEMICAL PHYSICS. 

in which the particles have some special arrangement, ex- 
pand unequally. With a given amount of heat the same 
substance always expands to the same extent ; but differ- 
ent substances, with the same amount of heat, expand un- 
equally. This may be shown by riveting together thin 
slips of two metals, for instance zinc and iron, forming a 
straight compound bar (Fig. 32). When dipped into hot 

water it is warmed, and the zinc, 
7 •••'••-•-•-•-• ■•.-.-.•■•■•:"? expanding most, becomes longest ; 
the bar curves, the zinc forming 
the convex side. If placed in ice- 
water, the zinc contracts most, and 

Fi«.32.-E S a^o n of Com- ^ ^ ^^ ^ ^ oppogite d j_ 

rection. 

59. Expansion of Liquids. — If sufficient heat is im- 
parted to a solid, cohesion is overcome, and the solid is 
converted into a liquid. Liquids, thus produced by heat, 
are also expanded by it, and to a much greater degree than 
solids. While iron, when heated from the freezing to the 
boiling point of water, increases by but s \ s of its volume, 
water expands ^, and alcohol ^ in volume. 

60. Expansion of Gases. — But liquids can not be in- 
definitely expanded, a sufficient amount of heat changing 
them into gases. As a rule, gases expand much more than 
liquids ; but certain liquids, as sulphur dioxide, are among 
the most expansible substances known. As there are no 
varying cohesions to overcome, gases expand very nearly 
alike, increasing from the freezing to the boiling point of 
water more than one third of their bulk. It has been 
found that gases expand ^-3 of their volume for each de- 
gree centigrade of increase in temperature. 

61. Measurement of Heat. — As the chief effect of heat 
is expansion, the measurement of expansion becomes a 
ready means of measuring the heat. The common instru- 
ments for measuring heat are called thermometers. They 
measure not quantity of heat, but temperature, or intensity. 



THKRMOMKTRIG 29 

A cubic foot of iron at the boiling-point of water contains 

manv times as much heat as a cubic inch, but the tem- 
po nit uro of both in the same. Liquids arc bel 

adapted as heat-m< khan either solids or gases; as 

M>lidfl the expansion is too alight to be easily perceptible, 
and gases ar nsitive to changes of atmospheric press- 

ure to tit them for this purp. 

Mercury has several important advantages as ■ ther- 
mometry tluid. It is readily obtained pure, and docs not 
adhere to the tube; it ifl sensitive to heat, expands with 

Jarity than most liquids, and has a range of 400 

0. between its freezing and boiling points. Temperatures 

below the freezing-point of mercury (40° below zero) are 

illy determined by thermometers filled with alcohol 
tinged with Borne coloring-matter to make it risible. As 

mercury boils at .'>.v> (..temperatures above that point 
• 1 by the expansion of air, or by the aid of 
thermo-electric currents. 

62. Mercurial Thermometer. To make this instru- 

fine glass tube, with a bulb at om 4 end, is partly 

filled with menury. The air is expelled from the rest of 
heating the bulb till the mercury boils; at the 

• when the vapor of the metal has completely 

driven out the air the tube is hermetically sealed by melt- 
.' tie- end of it with a blow-pipe. As it OOOlfl, the mer- 
cury tails in the tube, tearing a vacuum aboi 

63. Thermometric Scales. The sealed tube containing 
the menury is attached to 1 metal plate designed for the 
tie ihemical work, the 
diri directly on the glass tube. It is 
then dipped into ice-water, and a mark made on the pi 

■f the column of 11 led the 

dow introduced into boiling wafc 

Inch the column rises 1- marked M the 
-e are natural standard points whieh 
••as a ba-i- for the division of ti 



.a 



2/2— 
192— 



a 



30 CHEMICAL PHYSICS. 

In the centigrade thermometer of Celsius, the freezing- 
point is called zero, and the interval between that and the 
boiling-point is marked off into 100 equal 
spaces called degrees. In Keaumur's scale 
the same interval is divided into 80 degrees. 
6 The scale named after Fahrenheit, its in- 
ventor, and which has come into general 
use in England and this country, is not so 
simple. He divided the space between freez- 
ing and boiling into 180 degrees ; but, in- 
stead of starting at the freeziug-point, he 
tried to find the lowest possible cold, to 
make that zero. So, with snow and sal-am- 
moniac he got the mercury down to 32° be- 
low the freezing-point, and commenced 
counting there. On this scale, therefore, 
freezing occurs at 32°, and boiling at 212°. 
The several scales are distinguished by their 
Fig. 33. — Ther- initial letters F., C, and R. The centi- 
(SeT^penSx 6 ) grade, affording decimal subdivisions, is the 
most simple and rational, and has come into 
general use for scientific purposes. In all these scales, 
degrees below zero are distinguished from those above by 
prefixing the minus-sign ( — ). 




s 



§ 2. Changes in the States of Matter. 

64. Liquefaction. — Heat applied to solids overcomes 
their cohesion and changes them to liquids. That degree 
of temperature which is required to liquefy a substance is 
called its melting-point. From hundreds of degrees below 
zero up to thousands above, the various substances of na- 
ture melt at different temperatures, showing that each 
requires its particular amount of heat-force to throw it 
into the liquid state. 

65. Latent Heat. — In effecting this change, a certain 
amount of heat disappears, or seems to be used up in the 



SPECIFIC BEAT, ;U 

process. Aa this can no longer be detected by the sensed 
it has ceased to be sensiite heat, and is spoken of as latent 

heat If we take an Ounce Of ice at 32°, and one of water 

at 174°, and put them together, when the ice is melted, 

shall have two ounces of water at :>\?°. The ounee of 
hot water has, therefore, lost W'l of its heat in melting 
the ice, which amount is the M latent heat n of the result- 
ing water. The amount of heat thus consumed in altering 
the states of bodies, without raising their temperatures, is 
different in different cae 

66. Specific Heat. — If we expose equal weights of dif- 
ferent substances to the same source of heat, some will re- 
ro more than others. Water requires thirty times as 

much heat as mercury to raise an equal weight of it 
through the same number of degrees. Hence bodies are 
I to have different capacities for heat, and, as each sub- 
os to require a particular quantity for itself, 
that quantity is called its specific heat. 

67. Heat liberated by Freezing. — If the change of a 
solid t<> a liquid consumes heat, the reverse process must 

liberate it; the heat, therefore, reappears upon freezing. 

As the thawing of snow and ice in spring keeps down the 

nperature of the air, owing to a large amount of heat 

being used up in forming water, so, in autumn, the warm 

season is prolonged by the large quantities of heat that 
escape into the air from the changing of water into ice. 

68. Freezing Mixtures. —Advantage is taken of the ab- 
sorption of heat in liquefaction to produce freezing mixt- 
ures, the most common example of which is -alt and io& 

*his case the salt hasten- the melting <>f the ice. and 

a in the water thus formed. These changes require 

OUnf of heat, which is rapidly absorbed from 

:oundii._ . thus lowering their temperature. 

69. Boiling. When water is gradiialls heated, minute 

bul formed at tie- bottom of t: . which • 

a liul* nd disappear. Then- eon.-i apor or 



32 CHEMICAL PHYSICS. 

steam, which is formed in the hottest part of the vessel, 
but, as they rise through the colder water above, are cooled 
and condensed. As the heating continues, these mount 
higher and higher until they reach the surface and escape 
into the air, producing that agitation of the liquid which 
is called boiling or ebullition. 

70. Boiling-Point. — The temperature at which this 
takes place is called the boiling-point, and it varies with 
different liquids and in different circumstances. It is 
slightly influenced by the nature of the containing vessel. 
To glass and polished metallic surfaces liquids adhere with 
greater force than to rough surfaces ; and, before vaporiza- 
tion can occur, this adhesion must be overcome. Chemists 
put bits of rough marble into glass dishes in which water 
is boiling, so that small bubbles of steam may pass off, 
and thus prevent "bumping," or the escape of large 
quantities of steam at once, which might throw out the 
hot water and break the dish. 

It has been shown that the amount of air dissolved in 
water affects its boiling-point, as it presses the watery 
particles asunder, and thus aids them to take on the gase- 
ous state. Water freed from air by long ebullition has 
been heated to 135° 0. without boiling. When it did boil, 
the water was instantly changed into vapor with a loud 
explosion, the cohesion of its particles being suddenly over- 
come by the expansive power of the accumulated heat. 

71. Vaporization. — The change of solids or liquids by 
the action of heat to vapor is called vaporization. Sub- 
stances which are readily converted into vapor are said to 
be volatile, while those which can not be vaporized with- 
out decomposition are termed fixed or non-volatile. The 
slow formation of vapor from the surfaces of bodies is 
called evaporation. It goes on at all temperatures, even 
from the surface of ice and snow, but is greatly increased 
as the temperature rises, or as the pressure of the air di- 
minishes. 



VAPORIZATION. 

72. Heat of Vaporization. A much larger amounl of 
heal is spent or becomes Intent in converting liquids into 
vapors t han in changing solids to liquids, while the yap 

BO hotter than the liqnidfl from which the; arc formed. 

The heat has disappeared in producing the repellanl 

molecular motion and the consequent enormous expan- 

d of the gaseous body. If the liquid is exposed to the 

le to raise its temperature its 

tural boiling-point All the heal added after boiling 
mmencee ia earned away by the vapor. Water boiling 

violently is not S particle hotter than that which boils 

moderately. 

73. Latent Heat of Steam. The quantity of heal which 
appears during evaporation is very large. With the 

same intensity of heal it takes ;».} times as long to evapo- 
rate i pound of water as it does to raise it from freezing 

the water rooeivefl 5J times as much 

• in producing the change of state, and, 
of course, d trs as sensible heat. This quantitj 

there fo re, the "latent" heat of steam. If the pn 

o w ed , and the vapor is made to reassume the liquid 
f<»r:: The condensation of s pound 

of steam will raise .~>A pound- of water from the freezing 

■ he boiling point. The large quantity of heat given off 

-team in OOIldensing ifl utilized by means of steam 
.rat us in warming buildings. 

74. Cooling Effects of Evaporation. As evaporation 
consumes heat, it is a cooling process. We e\periei 
this in the ooU wmnarinn produced by the evaporation of 
water, or, in a more marked degree, by the evaporation of 

rfaoe of the hand. Tl 
_- from the dan i- s powerful 

I bodily temperature, while the vapor which 
escapes with tin- breath, by iti absorption of I thin 

ideraUe cooling i 
75 The Cryophorua, or Frost-Bearer, ifl so m 



34 



CHEMICAL PHYSICS. 




Fig. 34— The Cry 
ophorus. 



which strikingly illustrates this principle. It consists of a 
tube with a glass bulb at each extremity, one of which 
contains a little water. Air is expelled from the instru- 
ment by boiling the water, the aperture through which 
it escapes is then sealed, leaving the space filled with 
steam or vapor. The empty bulb is then placed in a 
freezing mixture (Fig. 34) and the vapor 
condenses, its place being supplied by vapor 
from the water-bulb above. Condensation 
and evaporation go on so rapidly that the 
water is soon frozen. 

76. Dew-Point. — The air always con- 
tains moisture, the amount of which varies 
with the temperature. The power of the 
air to absorb moisture is called its capacity 
for absorption. When it contains as much 
as it is capable of holding at a given tem- 
perature, it is said to be saturated, and any 
lowering of the temperature condenses it in the form of 
clouds, mist, fogs, dew, etc. The temperature at which 
the moisture is condensed is called the dew-point. If 
the temperature of the air has to fall but a few degrees 
before moisture is deposited, the dew-point is said to be 
high, and there is much moisture in the air; while, if 
the temperature has far to fall, the dew-point is low, and 
the air contains less moisture. It is obvious, therefore, 
that, by finding these two points of temperature, one can 
easily obtain the amount of atmospheric humidity. 

77. The Hygrometer. — This is an instrument for meas- 
uring atmospheric moisture. Daniell's hygrometer (Fig* 
35) is constructed on the principle of the cryophorus. 
The long limb ends in a glass bulb b half filled with ether, 
into which dips a small thermometer. The bulb a on the 
short limb is empty and covered with muslin. The tem- 
perature of the air is shown by another thermometer, c, 
fixed to the stand of the instrument. When an observa- 



ELASTIC P0RC1 ov VAPOR& 



8fi 




Daniell'i 1 

IllCUT. 



tion is to he made, a little ether is ponied upon the mus- 
lin, and, as it evaporates, the temperature of the other 
bull> li reduced. When it is 

sufficiently oooled to condense the 

store of the air, it will be covered 
wit}; dew. The thermometer in the 
tube b shows at what temperature this 
deposition takes place, and, of course, 

- the dew-point The greater the 
difference between the reading 
the two thermometers the less moist- 
ure there is in the air. The propor- 
tion of moisture in the air of our ar- 
tificially-heated rooms ifl a matter of 
importance to health, and the 

ifl very valuable in ena- 
bling us to determine it. 

78. Volume and Density of Vapor. — Equal hulk- of 
different liquids generate unequal volumes of vapor. W a- 

. ields a larger amount than any other liquid. While 
a cubic centimeter of water gives 1,660 cubic centimeters 

of Vapor, a cubic centimeter of alcohol yield- 528, One of 

ether 298, and of oil of turpentine L93. The density of 

increased either by cold or pressure. The de- 

• '.Inch its temperature can not be further lowered 

without its changing to the liquid state is its point of 

U nsifij. 

79. Elastic Force of Vapors.— All vapors ire elastic 
and have a tendency to diffuse throng] erting 

• or less force againal any obstacle. This expansive 
power of called their 

through the vap 
r, i- the power that drives I j ine. 

80. Distillation quid bj heal 
in one vessel and condem by cold in another | 

. be either i i liquid 



36 



CHEMICAL PHYSICS. 




Fig. 36.— Distillation. 



non-volatile substances dissolved in it, as in distilling 
water, to purify it, or to separate two liquids which evap- 
orate at different temperatures, as alcohol and water. In 

the latter case the heat is carried 
just high enough to vaporize 
the most volatile liquid. The 
product of the process is called 
the distillate. When solids are 
vaporized, if the vapor on cool- 
ing assumes the solid state with- 
out becoming a liquid, the pro- 
cess is termed sublimation and 
the product a sublimate. 

81. Condensation of Oases. — 
When a gas loses heat enough to change it to the liquid 
or solid state it is said to be condensed. Under the joint 
effect of pressure and extreme cold, even those gases once 
considered permanent have been reduced to liquids and 
some to the solid condition. Dr. Faraday invented a very 
simple method for condensing gases. He placed the mate- 
rials from which the gas was to be generated in one end of 
a glass tube bent in the middle, which was then hermeti- 
cally sealed (Fig. 37). The expanding 
gas confined in so small a space ex- 
erted a tremendous pressure, the force 
of which condensed a portion of it into 
a liquid in the other end of the tube, 
which was immersed in a freezing 
mixture to facilitate the process. By this method he suc- 
ceeded in liquefying carbon dioxide, chlorine, ammonia, 
and several other gases. Within a few years, MM. Cail- 
letet and Pictet, by means of elaborate apparatus for pro- 
ducing great pressure together with low temperature, have 
succeeded in liquefying oxygen, nitrogen, and hydrogen, 
which had long resisted all attempts to condense them. 
82. Heat and Chemical Action. — Besides these physi- 




Fig. 37.— Condensation 
Tube. 



TllK NATURB OF HJ :;; 

eal changes, heat is also employed to effect innumerable 

chemical changes. By means o{ lamps, hat lis, ami fui - 

naces, the chemist is able to subject bodies to varying de- 
es <>f temperature ami to promote ami modify their 
tdon on each other. By its repellent influence upon the 
nstituenl parts of matter, heat overcomes ehemieal at- 
traction, d< om])oumls, and brings new affinities 
into play, thus producing new substant 

/" \ $0/ Halt. 

83. The Caloric Hypothesis.— In the foregoing brief 

Statement of the actions and effects of heat we have con- 
fined ourselves to facts which can he shown by experi- 
ment, ami have spoken of heat merely as a force or avvnt. 

• how are its effects produced? It was long regarded 

as a kind of matter — a Bubtile fluid — an imponderable ele- 

•it, whose entrance into OUT bodies produces the feel- 
ing of warmth and its escape that of cold. This fluid 

was supposed to he stored up in the interstices ol 
•ten some kinds holding more than others, according 

to their various capacities. It was assumed to have an 

attraction for the particles of matter and to combine with 

'ii, while its Own partic]. -elf-repul>ive and thus 

ised the atoms with which they united to repel each 

other. This notion of the materiality «»f heal is m»w 
mdonecL 

84. Grounds of a New Theory.— ('mint Etumford in 
the last century brought <>ut many tacts vrhicfa W( 

wholly inooi with the calorie hypothesis, and many 

others of similar import have since been observed- If an 

iron -truck upon an an\il it- temperature is rail 

. hammering Prill make it red hot 'I 

rubbed together till they tak 

gitated by friction till it 1m.i1-. I* 
eral law that arrested mechanical motion produces hi 
and thai amount of beat produced depends no! 



40 



CHEMICAL PHYSICS. 



CHAPTER V. 



ELECTRICITY AND CHEMICAL CHANGE. 




Fig. 38.— No Effect. 



88. The Voltaic Current. — Among the methods of pro- 
ducing electricity there is one which is closely related to 
chemical action. It was first discovered by Galvani, and 
has been called after him galvanism ; but its most illus- 
trious cultivator was Volta, from whom it is also named 
voltaic electricity. A strip of zinc and 
one of copper are placed in a vessel 
containing water, to which has been 
added a little sulphuric acid. If not 
permitted to touch each other, as in 
Fig. 38, there is little or no effect. 
But, if brought into contact, as seen in 
Fig. 39, several results ensue. The 
acid in the water grows weaker ; the zinc strip is corroded, 
and bubbles of gas are seen to escape from the surface of 
the copper. If the metals are separated, the action ceases ; 
and, if this is done in the dark, a minute 
spark may be seen. Electricity seems to 
flow round and round in the direction of 
the arrows, like an invisible stream. The 
circulating force is termed an electric or 
electromotive current, and the combination 
through which it passes a voltaic circuit. 
The electric current originates in chem- 
ical changes, and requires a compound 
liquid capable of decomposition by one of the metals. 

The source of the electricity, in this case, is the decom- 
position of the sulphuric acid forming zinc sulphate, and 
setting free hydrogen gas. The zinc sulphate being dis- 
solved in the liquid, the plate is kept clean and the action 
maintained, till the metal is consumed, or the acid all 
neutralized. 




Fig 



The Vol- 
taic Circuit. 



VOLTAIC BLBOTRIGITY. 4 1 

ctricity is also produced by contact of any two met- 

and a liquid t hat acts more powerfully upon one metal 

than upoD the other. Hut their is a irreat difference as 

to the lifferent metals when thus 

The metals and earhon have been arranged 

in i > ording to their electro-motive force; the 

moet remote from each other in the following 

list, for instance one and carbon or sine and platinum, 

- —intermediate couples, Buch as 
iron and copper, affording comparatively weak ones; 

l. Zinc 4. Niekel. ;. Gold. 

Lead. 5. Copper. & Platinum. 

3. Iron. Silver. D. ( larbon (graphil 

89. Electrodes. — To the plates are often soldered wires 
with terminals of platinum to withstand the action of cor- 
rosive liquids. The ends of these wires are known as the 

poles of the Circuit, from an idea that they exerted an at- 

tivr and repellent action, like the poles of I magnet 

raday proved that there is no attraction or repulsion 

in the case, and bed the better term electrodes^ which 

ins simply a door or way for the electricity. The cop- 

pole is termed positive^ and the zinc pole n> 

90. The Voltaic Pile. — The power of the circuit may 
be increased by repeating its elements. The pile invented 

by Vblta and named after him was the first 

trivance U>v augmenting the force of the /j "" i' 

trie current. It is made by preparing m ^ m * 

ill plates or disks of metal, usually copper ^mmk j 

.'id placing 1 them pieces of \ UB| ( 

inel moistened with an a -aline Bolu- 

Such I in Pig. 10. 

■ b is pis d the m 

:iui i- p re s er ved. Commei 
at the bottom, I 

zin -me], /.i: 

and so rv .. r ■ hundred sets, as d 



_ 




42 CHEMICAL PHYSICS. 

The lower or copper end is positive, and the other nega- 
tive ; a current, therefore, moves in the direction of the 
arrows. This form of instrument gives a strong effect at 
first, but rapidly declines in power. 

91. The Galvanic Battery. — To augment the electric 
effect, and at the same time secure steadiness of action 
and convenience of management, the compound circuits 
are arranged in forms known as voltaic or galvanic bat- 
teries. A series of vessels, called cells or elements, con- 
taining an acidulated liquid, is arranged in each of which 
there is a plate of copper and another of zinc ; the cop- 
per plate of one cell being 
connected by a copper wire 
with the zinc plate of the 
preceding cell (Fig. 41). But 
even this arrangement proved 
objectionable, inasmuch as 

Fig. 41.— Voltaic Battery. J . . ' ,.,-,, 

the zinc is soon dissolved by 
the acid, a circumstance which led to the construction of 
the so-called constant elements. It was found that, by 
coating the zinc with mercury (amalgamating), it better 
resists the dissolving effect of the acid ; moreover, it was 
discovered that hydrogen which is set free at the copper 
pole is liable to collect as a layer on the surface of the 
metal (copper), rendering it inactive. A second liquid, 
therefore, was introduced into the cell, which, by chemi- 
cal action, removes the hydrogen. Upon these principles 
are based the constant elements of Daniell, Bunsen, and 
Grove. 

92. Quantity and Intensity. — In the battery the quan- 
tity of electricity depends upon the size of the plates ; the 
intensity, upon the number of them. If we increase the 
size of a pair of zinc and copper plates, we increase the 
quantity of the electricity they produce, but not its inten- 
sity ; while, if we reduce the size, we reduce the quantity, 
the intensity remaining the same. On the contrary, if we 



. KOLYSIS, 



i:; 




multiply the number of pairs (oells) of equal rise, kh< 
tensity ifl augmented at an equal rate, while the quantity 
is unchanged. The eleo- 

i by a 

edingly 

feehle ; the seeoud cell 

- no more to it, luit 

intensifies its power. In 

urrows illus- 

. ru unulating Int. -n-u v. 

cumulating 

intensity. Pot sustained effects, as in chemical deoom- 

ons and telegraphy, where vasl quantities of eleo- 

required, the battery is employed, its current 

to the requisite tension by multiplying the 

evils. 

93. Electrolysis. — If the cuds of the platinum w 
connected with a battery are placed near each other in a 
Teasel of i mtaining a little sulphuric acid to aid 

conduction, bubbles of gas will be >rru to 

from the terminal- and escape at the 
A couple of L r la« tubes tilled with 

rted in the vessel oyer the 

poles, serve to collect the n 

. whioh, upon examination, prove to 
pure hydrogen and purr oxygen, the hulk 
of the former being twice that of the latter. 

Th. (-•- i- the wanr which 

is decomposed. T. 

and 
pable <»f ' om- 

called an 

94. Positive and Negative Elements. \^ om- 

found ii 

ii, rhloi 

phur, appear at the positive el 

i the 




KU-c- 



4,4: CHEMICAL PHYSICS. 

metals, appear at the negative electrode, and are called 
electro-positive. Oxygen heads the first list, or is the 
most powerful electro-negative body, while potassium 
heads the other, being the strongest electro-positive sub- 
stance. The elements may be arranged in such an order 
that each will be electro-negative to all which follow it, 
and electro-positive to all which precede it. As the elec- 
tric current thus originates in chemical changes and pro- 
duces them, and as the atoms seem to be in opposite 
electrical states, it is obvious that electrical force is very 
closely allied to chemical power. 

95. Electro-deposition. — When certain compounds of 
copper, silver, nickel, or gold are dissolved in water, if a 
current of electricity is passed through the liquid, it de- 
composes the compound in solution, and the metal is de- 
posited. In this way medals and pages of type are cop- 
ied (electro-type) ; and new metallic surfaces are imparted 
to articles, as in electro-gilding and electro-plating. 



CHAPTEK VI. 

LIGHT AND CHEMICAL CHANGE. 

96. A Third Radiant Force. — Besides the heat-rays, 
which take effect upon all kinds of matter, and the lumi- 
nous rays, which act only upon special forms of nerve- 
substance producing the sensation of vision, luminous 
bodies send out a third class of rays which act upon cer- 
tain chemical substances, producing combination and de- 
composition. These are called actinic or chemical rays. 
They accompany the light of the sun, and are produced in 
artificial illumination. The art of photography depends 
upon them, and has given a great stimulus to their investi- 
gation. Like light and heat, the chemical radiations are 



RADIANT KOK 






measurable in their effects, and have given rise to an in- 
dependent branch of scientific Inquiry. 

97. Refrangibility of the Invisible Radiations. -The 
heat -rays and the chemical rays are reflected ami refracted 

like light, ami like the colored rays they exhibit marked 
differences in their degrees of refrangibility, When the 

in is passed 

through a prism 

( Pig. 11 t not only 

is there an ob- 
long visible image 
thrown upon the 

. 'lit there 

a >an invisible 

heat - image, and 
an invisible chem- 
ge, irhich 
are revealed in 
different ways. 
The position and 
varying intensity 

Of the fa 

tram may he 

traced out by a 

delicate ometer, ami it is found that it begins down 

in the neighborhood of a, and runs up into the lumino 

region. A large portion of the heat-rays are hei 

lower refrangibility than the red, and are dark radiati 

If, now, a solution of diver nitrate u trash< d over i lai 

. which u then placed upon i 
rer» ipectrum and extend through th< 

nical change takei place npon ita 

dich deflnee the outline of the 
il s|M*ctruni. [( i found that tie- chemj 

s are m« ble than the lumin< 

while the black ikei place in fchi m. 




qj ( .f the Three Spectra. 



46 



CHEMICAL PHYSICS. 



it extends also through the dark space up to b. That the 
heat of the spectrum is greatest in the red, and that there 
are dark thermal rays of still lower refrangibility, was 
shown by Sir William Herschel. in the year 1800. That 
the chemical rays of the luminous spectrum are most act- 
ive in the violet region was pointed out by Scheele, in 
1777 ; while their extension into the dark space beyond 
was discovered by Bitter, in 1801. 

98. Distribution of the Forces. — The forces of the spec- 
trum are thus very unequally distributed, as is illustrated 
in Fig. 45, where they appear to rise like the peaks of 




Fig. 45. — Varying Intensities of the Spectrum Forces. 

mountains. The middle curve shows the varying intensity 
of the luminous force. The maximum is at B in the yel- 
low space, and from this point the intensity of the light 
rapidly declines each way ; its extent being shown by the 
space shaded with oblique lines. The curve ^4, with the 
vertical lines, represents the position and varying force of 
the heat ; and the curve (7, horizontally shaded, exhibits 
the distribution and unequal energy of the chemical force. 
The three maxima are widely separated, and it is notice- 
able that where the light is strongest the chemical force 
seems quite neutralized. 

99. Actinometry. — It has been stated that the force of 
the chemical rays is measurable, and for this important 
step of research we are indebted to Dr. J. W. Draper. If 
hydrogen and chlorine gases are mixed in equal proportions 
in a glass vessel, and kept in the dark, they will not com- 



EFFECTS o\- Tin: CHEMICAL BUI S 17 

bine; but, if exposed to the light, the] unite with each 

other, forming a compound. Upon such a mixture, how- 

p, the red rays produoe no effect, while the violet n 

a to oombine explosively. U is the ohem- 

at ore here active, and Dr. Draper employed a 

mixture «'t' these gases t«> test, by the rate <>f combination, 

the varying intensity of the force. Instruments for this 

purpose have been called actinometers* 

100. Variation of Strength in the Chemical Rays. — 
ations have given evidence that the effeol of chem- 
ical rays varies with the Beason and with the time of day. 
At noon, in summer, and especially in the month of July, 
their strength is greatest Traveling southward we find 
chemical action decreasing, though the light beoon 
inore brilliant and the heat more intense. 

101. Relation to Vegetation.— ( >f the effects produced 
these rays in nature little is understood. It has lon«j 

an known that light exerts a powerful influence upon 
the organic world. Vegetation languishes in the absence 
of light, and flourishes when exposed to it. It was at Him 

supposed that this power over plants resided in the chem- 
ical rays; but it is now known that the force that decom- 
poses carbon dioxide in green leaves, and which is the 
foundation of the vegetative pr . is mosl active, not 

in the violet, but in the yellow apace of the spectrum, 
• the actinic for ent 

102. Chemical Reactions of Light, tl was l<>tiL r sup- 
posed that the chemical pays art only upon a ten sub- 

. but the central illy the fact. Bo many Bub- 

i l»v them, and in so many different 
way-, that BOme think B I upon 

olid without impressing u] endur- 

ing molecular change. Pour kind tnaj be I 

referred to i Pint, the elements, such 

. their allotropic for 
■i\ promotes chemical combination <>f the . l.-m 



48 CHEMICAL PHYSICS. 

already shown (99). Third, it produces mechanical 
effects. If the beautiful ruby-colored crystals of arsenic 
disulphide are exposed to light for some months, they 
soften and fall to powder. Fourth, chemical compounds, 
such as silver salts, are decomposed under the influence 
of light, and new compounds are formed. 



CHAPTER VII. 

SPECTRUM ANALYSIS. 

103. Interest of the Subject. — With the remarkable 
discovery that actinic radiations can produce enduring 
images by the chemical alterations of matter, it was 
thought that the marvels of light were exhausted; but, 
twenty years after photography, came spectrum analysis 
— the most brilliant and startling of all modern discov- 
eries. It has endowed the chemist with a power of re- 
search of hitherto unapproachable delicacy, by which new 
elements have been discovered, and our knowledge of the 
composition of matter greatly extended and refined ; and, 
what is much more astonishing, it has revealed the chem- 
ical elements in the atmospheres of the sun and the stars, 
and thus made chemistry a cosmical instead of a terres- 
trial science. 

§ 1. The Luminous Spectrum. 

104. The Analysis of Light. — By a triangular prism of 
glass, or other transparent substance, ordinary white light 
is decomposed into a series of colored lights. A ray of 
light from the sun, passing through a prism (Fig. 46), is 
dispersed, and produces an oblong, rainbow-colored image 
called the solar spectrum. White light is, therefore, held 
to be a compound consisting of these colored lights, which 



SPECTRUM ANALYSIS 



49 



irated by the prism. Bach «M»l<»r has its own pi 
utgibility, pree of divergence from the line 

ii by the original ray, 
the /•<// being the least re- 
fracted, and the n< 
most 

105. Newton's Exper- 
iment. 8 ral phenom- 
.. as setMi in rainbow- 
tints, in the sparkle <>f jewels, the chromatic flashes of cut 
188, and tin* gleaming hues of clouds at sunset, have ever 
been familiar: bnl they were first explained by Newton in 
his treatise on optics over two hundred years agio, lie 
. that white light, in passing through the prism 




Pig, 10. Decomposition ol I 




UBM 



lolved into its el forming a splendid 

own in the plan- at the beginning <»f 

the volume. Thu • -s.-. If 

the combined by a l< 

ill u - i of n bite 

106. The Solar Spectrum. The eol< 
ire nit i ii Tim 

sola in the highesl <\<L r r>>- brillianl and 

pun v blend with each other in itnperoeptifa 



50 



CHEMICAL PHYSICS. 




Fig. 48.— Effect of Second Prism. 



dations, so that their number and limits are indeterminate. 
For convenience they are designated as forming seven 

principal groups ; but, as 
Baden Powell remarked, 
" the fact is, the number 
of primary rays is not 
really seven but infinite." 
That the colors produced 
are incapable of further 
decomposition may be 
shown by passing a beam 
of the spectrum through 
a second prism, as repre- 
sented in Fig. 48. The white ray refracted or bent by the 
prism, /?, gives the spectrum on the screen, A B. If, now, 
an aperture is made in the screen, and a colored beam 
passed through a second prism, P, it will not be further 
analyzed, but only changed in its 
course. 

107. Spectrum of the Electric 
Light. — Any source of light may be 
employed to produce a spectrum ; but 
next to the sun, which is by far the 
most brilliant, the spectrum of the 
electric light is most powerful, and is 
generally used when intense effects 
are required. Thus a piece of sodium 
may be volatilized by placing it on 
the lower carbon of an electric lamp, 

as shown in Fig. 49. Fig. 49.— Electric Arc. 

§ 2. The Spectroscope. 

108, Its Essential Parts. — The spectroscope is an in- 
strument for observing the spectrum. Fig. 50 shows its 
simplest form, and the relation of its parts. L represents 
the light, which may be from any source, natural or arti- 



^■1 




THK SPECTROSCOPE 






fi« i:il. the Bpectrum of which ia to be examined. i 

closed at t, but in the end of which there ia a rertt- 



f 




iy, ■.'. n Bimpl Bp i toon 

eal slit, opened an<l adjusted by a slide or screw. This 
slit is a very important part of the instrument, and ifl 

formed by knife-edgea of the mod unchangeable material, 
finished with great accuracy, so as to give a perfect line, 

though n<»t more than 3i t ( , of an inch in width. The light, 

entering the slit, passes through a tube called the collima- 
tor, .1. containing a lens, by which the raya are made par- 
allel before falling on the prism, /\ The raya era 
refracted from the opposite hoe of the prism, yel only 
_ r 1 1 1 \- difl . bo that the Bpectrum, >', ia but little 

larger than the width of the slit. In order t<> observe it 
of a sufficient size, at a short distance, a magnifying 
or small telescope, I\ ia employed. The collimator, the 
prism, and ore the essential parts; 







52 



CHEMICAL PHYSICS. 



and in use the prism requires to be covered to exclude in- 
terfering light. 

109. Measuring the Spectrum. — But for scientific pur- 
poses the instrument requires the most accurate means of 
measuring the spaces of the spectrum. For this purpose 
a third tube has been added, as shown in Fig. 51 at S. 
At its outer end there is a glass plate, m y upon which is 
engraved or photographed a scale of minute divisions. A 
lamp, K, throws the image of this scale through the tube 
and lens, so that it falls upon the face of the prism at n 
at such an angle as to be reflected by the polished surface 
of glass through the telescope, F, to the eye. Parallel 
with the scale the observer sees the spectrum of whatever 




Pig. 52.— The Common Mounted Spectroscope. 






DIRECT VISION SPECTROSCOPES. 



53 



light ifl employed, and can thus fix and compare the po§i- 

>ntispie< i 

110. The Mounted Instrument. — The foregoing fig 

the parts for explanation ; Pig. 

struetion ol the instrument as ready 

the oollimator-tube, the alii not being risible. 

d aa the Bouroe of light ; and a 

i an an mpporting in 

ired to experiment with. 

; with a goard to screen the 

light ( ifl the tube with the BcaL 

lie for projecting the im 

111. Direct-Vision Spectroscopes.- It La obviously an 

have th< i telescope i 

so 
that tent 

be applied di- 

Thia 

1 in 

bining seYeral prisma ol and flint-glass in the 

main. m in Pi 9 p representing crown-] 

flint-glass p 
inal direction ol tfa 

tlni ad combined witli 

!:iss funi 
ion 

ed from 

1 in a Miiall, 

■ 







Bf Rav. 




54 



CHEMICAL PHYSICS. 








O 



->* 



M 



§ 3. Dark Lines in the Spectrum. 

112. Fraunhofer's Work.— 

The solar spectrum seen at the 
top of the frontispiece in this 
book is crossed by dark lines, 
which are always seen when sun- 
light is examined with a spectro- 
scope. These lines were discov- 
ered by Wollaston, in 1802, but 
were first carefully studied and 
mapped out by Fraunhofer, a 
German optician, and are gener- 
ally called Fraunhofer's lines. He 
counted 590 in the visible spec- 
trum, and in his map of them 
(Fig. 55), marked the most im- 
portant ones by the letters of the 
alphabet. Fraunhofer further 
found that the lines did not vary 
in sunlight, examined at different 
times ; that the reflected light 
from the moon, or from Venus, 
gives the same distribution of 
them as the sun, while the spectra 
of the fixed stars differ from those 
of the sun, and from each other. 
From these facts he drew the im- 
portant conclusion that the cause 
of the dark lines in the solar spec- 
trum exists in the sun, although 
what that cause could be seemed 
an impenetrable mystery. 

113. Dr. Draper's Investiga- 
tions. — The next important step, 
after Fraunhofer, was taken by 



DISCONTINUOUS BPKOTRA. 

Draper. He was the Orel to use Frannhofer'fl 

mtry, modifying it, in 1842, in such i 
manner a> to cast the fixed lines upon the sensitive surfa 
of ] iphic plates. Be published a map of the i 

ing f<»ur these lines beyond the 

limit of the violet ray, and probably doubling t ho number 
of lines thm known. But, what is nuuv important, he 
passed to the examination of spectra formed by inoandes- 
• rial bodies, and discovered a principle which 
indamental in the philosophy of the subject Ele de- 
termined the temperature at which a solid body begins to 
ihowed that it is the Bame for all solids; 
that, as the temperature increases, the oolored rays arc 
emitted in the order of their refrangibility, from red up to 

viol that the all incandescent solids are 

. or without lines or breaks. 
114. Spectra of Gaseous Bodies. - Bui when a body 
volatilized its spectrum is changed, breaking up into 

and these lines 
not dark, hut blight, and of various colors. If a little 

into the gas-flame ( V\ the 

flame is Colored a bright yellow, and if the spectrum is 

l»o, a bright yellow line 
of lighl will appear, always in the Bame position (Front 

:el, if a higher dispersive power is applied, this 
yell Ived in1 forming the double 

line Lb the dial A mark of 

diunL If, now, potassium is submitted to the Bame, 
[violet, and thr two i 

•rum, and a \ ioh-t line 

og darkness ( Pront If 

h pure h. 
nit 

vn in t «•••. Ti f the lii 

are as i and the num- 

:" the lines i ii an imiro 



56 CIIEMICAL PHYSICS. 

while sodium gives but two lines, iron yields several hun- 
dreds. 

115. What the Lines indicate. — The spectral lines in- 
dicate, first, chemical identity, and serve as tests of chem- 
ical substances. Each element gives a peculiar spectrum, 
distinguishable from all others in the number, color, 
breadth, and grouping of its lines. So distinct are they 
that when a compound is vaporized all its elements are at 
once disclosed. If several substances are volatilized to- 
gether, all the spectra can be identified. Most of the lines 
are mere films, like the finest spider's web, so that they 
really occupy but a very small portion of the spectrum 
space. In some cases, however, several of the bright lines 
of different bodies seem to coincide; but upon closer 
scrutiny these have been generally found to show real 
though slight differences of refrangibility. 

116. What are the Spectrum Lines? — The optical an- 
swer to this question is, that they are images of the slit. A 
slit of say the fiftieth of an inch would, of course, give on 
a screen a very fine white line, which would be simply an 
image of the aperture. Now, if that filmy ribbon of white 
light is passed through a prism, the spectrum formed will 
be a succession of colored lines into which the white line 
has been resolved, and the whole spectrum will be but a 
series of images of the slit, either continuous or broken. 
It is easy to recognize that the bright-colored lines are 
images, but it may be asked, What are the dark solar lines 
images of ? Darkness is absence of light, and the dark 
lines of the spectrum simply indicate the absence of lumi- 
nous rays. It is sometimes supposed that there are dark 
lines of gossamer delicacy in the sunlight, but this is a 
misconception. There are rays wanting in the sunlight, 
and in the spectrum these vacancies come out as lines of 
darkness. If the slit is changed to a cross, then, as the 
mark of sodium, we have a yellow cross, instead of a line, 
and black crosses in the spectrum of sunlight. 



FRAUNHOFEIfS LINES. 



57 



117. Fraunhofefs Lines explained. — The tad 
doable dark line exists in the solar spectrum jusl wh< 
thedou ;lit line oooars in the spectrum of Bodium 

v attracted attention. The cause of the dark lii 

:>v Kirchhoff in L859. Se found thai the p 

ips and systems ol them coincided - 

th the positions oi groups <>f bright lines produced 

itrial substances (F The uezl 

>very that, when Lighl passes through 

and then through the prism, the spectra 




exl k lines which vary according to the vapor used 

Hence it : known that vapors hare the power ol 

a in the beam ol lighl 

sent tii ! ind that th 

wh: which thai 

- iin vapor ■ How Light, 

ha brum ol 

a iKN'im of sunlight haying -lark lino in place <»f tin- 
that ti. in- 
:i an atmosphere which 001 

v tion thai 

a d 



58 CHEMICAL PHYSICS. 

metals must be in a volatile state, which implies an atmos- 
phere surrounding the sun and laden with metallic vapors ; 
this is called the chromosphere. Below this there must be 
a liquid or solid nucleus of far greater heat, the main 
source of illumination, and that yields a continuous spec- 
trum ; this is called the photosphere, or light-giving stra- 
tum. As its light shines through the atmosphere above, 
or chromosphere, the metallic vapors intercept the rays 
which they can themselves emit, and thus fill the solar 
spectrum with dark lines, or lines of absorption. 

§ 4. Spectroscopic Applications. 

118. Delicacy of the Chemical Indications. — Spectrum 
analysis affords a ready, certain, and delicate means of 
testing chemical bodies. There are various rare metals 
which resemble each other so closely that they are distin- 
guished with difficulty by the ordinary tests ; but, how- 
ever mixed together, or with other substances, when 
vaporized their characteristic spectral lines are detected 
at a glance. The amazing sensitiveness of the reactions 
has led to new results which would once have been re- 
garded as incredible. The spectroscope will detect the 
one eighteen-millionth of a grain of sodium, and it has 
shown that common salt, which contains sodium, is almost 
omnipresent. It pervades the dust of the atmosphere, 
and is taken into the lungs with the breath. If we clap 
our hands, or shake our clothing, or jar the furniture, 
the dust set in motion contains sodium enough to affect 
the flame and give its reaction in the spectrum. Again, 
the six-millionth part of a grain of lithium is sufficient to 
reveal its beautiful red line, and it would be detected 
though mixed with ten thousand times its weight of other 
substances. It was formerly regarded as a very rare ele- 
ment, known to exist in only four minerals; now it is 
found almost everywhere — in the juices of plants, fruit, 
bread, tea, coffee, wine, tobacco, milk, and blood ; also in 



W iHK SNB0RO8OOPE, 59 

meteori .and the water of the Atlantic. I>r. Miller 

found that the stream i ring poured it hun- 

dred }><>und< <>f lithium «*hl« »ri< 1» - every twenty-four hoi 

119. New Substances. Thai which had 
hit: [ chemists should be caught by th rum 

■iK in examining the 
from the Bolid matter in the water 
a sprim;, at Purkheim, noticed BOme new lines, from 
which he inferred a oei II- accordingly 

NT tons of the water, and from 
two hundred grains of what turned 
the chloride of a new metal, which he called 

ctBsiuin, from its blnish-gray spectral line. Three other 
metals, unknown, and named Rubidium, Thallium, 

and Indium, from the colors of their lit: 
ntly found by the same i 

120. The Spectroscope in Steel-Making. — In the M Bes- 

■.•<s" for inakinir steel the atmosph( _vn 

barm the carbon and rili m themolfc 

iron, and the heated gat in flame al the mouth of 

The operation must be Btopped at a i 
md if it h don 
whole t Bed- The flame changes with 

th. H of the combustion, and, although a quick 

irlv when the 
time ha.- COl top the bl 

a which the carbon disa] 

1. 

121. Spectra of Organic Substances. The in 

ra of organi - produ 

I he abeorptiye action 

fruitful, and pr 

are identified in • the 

at*< 

be 



60 CHEMICAL PHYSICS, 

detected in which the spot contains only the thousandth 
of a grain of blood, and is fifty years old. Again, this 
process has been made to throw light on physiological 
changes, such as the circulation, and the rate of diffusion 
in the animal system. Dr. Bence Jones injected salts of 
lithium under the skins of Guinea-pigs, and then by the 
combustion of the tissues, at different times, the appear- 
ance of the red lithium line showed the rate of diffusion 
of the substance. Three grains being thus injected, in 
four minutes it was found to have made its way into the 
bile and the aqueous humors of the eye, and in ten min- 
utes traces of it were detected in the crystalline lens, 

122. The Tele-Spectroscope. — But by far the most im- 
pressive application of spectrum analysis is to the heav- 




Fig. 57.— Spectroscope, with Train of Prisms. 

enly bodies. An instrument adapted for this purpose, 
and attached to the telescope, is called the tele-spectro- 
scope. Fig. 57 represents the one employed by Prof. C. 
A. Young, of Princeton College, in his solar researches. 

123. Elements in the Sun. — The principal constituent 
of the sun's chromosphere is hydrogen gas, which is always 
present, as shown by the length and brilliancy of its spec- 
tral lines. The solar prominences are regarded as local 
accumulations of the chromosphere, which seem to force 



BLKKNTS in PHI BUN. 

their way up from the interior of the boh with great i 
lenoe, in the form of monster eruptions, which con 

mainly of incai 

arbon, in the Bun, 1- - 
;im reveals the follow ii.. 
atom d by Prot Efa 3 

l. Sodium. 5, Iron 9. Zinc L3. Rubidium, 

alcium. 6. Chromium. 10. Strontium*] L V 

•'». Barium. ', \ IteL 1 1. I admium. 1~>. Aluminum. 

tgnesium. s. Copper. L2. ( 'obalt L6. Titanium. 
These i at in i condition of strongly heat 

luminous vapor, most abundant in the Ion the 

at many ol 
them are thrown up to great 
jjhta in the promin* 

y, no doubt, 
und< snaation by 

_. and pour back upon 
the liquid ph 

ol metallic rain. 
IV..;". S that sul- 

phur Lb probably present in 
and 1 races 
Ol other <•!■ 

irhicfa « ad to 

no knon ' : rial Bui 

124. Elements in the Stars. Light is the same through- 
out the risible m nature ie not cl y the 
i wlii<h it travels. In the case <>f the 
with radiati stly weakens 

lerful d< I the 

tests, been lately proved that both 

M itli the M«llar light. \\ 

Res, still furt 

the Kin. 




62 CHEMICAL PHYSICS. 

upon earth, and in the sun, are found also in these dis- 
tant bodies. Spectrum analysis thus adds its powerful 
evidence to that already existing, to show that the stars 
are suns, similar in constitution to our own. 

Only a meager outline of spectrum analysis has here 
been given, and it can convey but an imperfect idea of the 
extent, precision, and surprising harmony, of the knowl- 
edge that has so quickly arisen upon this interesting sub- 
ject. Those who care to pursue the study further are 
referred to the works of Schellen, Koscoe, and Lockyer. 



PART II. 
OHEMIOAL PRINCIPLES. 



OHAPTEB VIII. 

LI ( ■HAKAi IBB OF < II BMIC \ L kOTIOK. 

125. Bavtkg briefly considered the molecular foi 
whi«h determine the forma and states of matter, and vari- 
ously influence chemical phenomena, we may now take up 

itady of chemical changes themselves. There arc, 
iin elem< !acts and princip] rning 

these cha ! leading to importanl theoretical i 

which it is n , to consider before explaining the 

of chemistry or entering upon a descriptio 
deal robe 

126. Elements and Compounds.- A a the letters oi 
alphabet make up all the words, sentences, and books of 
abngoag -mall number of chemical elements oom- 
poeeall t , and many thousand arl ificial 

chemical experiment All chemical 
chain n producing, altering . OOm- 

iou of compound bodies Into simpler 
is called ompound >r in- 

•ailed p\ 

into 

. and th- 
and i Thii i- called uli 

substances can i Further 



64 CHEMICAL PRINCIPLES. 

therefore known as elements. Qualitative analysis deter- 
mines of what elements a compound consists ; qua?itita- 
tive analysis ascertains the proportions of these elements. 
Synthesis is the reverse process, by which simpler bodies 
are built up into those of greater complexity. At the 
present time only about seventy of these simplest forms of 
matter have been brought to light, and concerning the 
existence as elementary bodies of two or three of these, 
chemists are not yet quite agreed. A complete list of the 
elements, including those which are still in doubt, is given 
in the Appendix. 

127. The Chemical Force. — Affinity, chemism, or chem- 
ical force, are names given to that power in nature which 
unites elements into compounds. It acts only at insensible 
distances, or when substances are brought into the closest 
relation with each other ; but its effects are numberless, 
easily seen, and of the highest importance. It is an ener- 
gy of the natural world acting upon all forms of matter. 
In the production of its effects, the chemical force con- 
forms to exact and inflexible laws, forming a science 
equally remarkable for the beauty of its principles and the 
practical value of its applications. 

128. Characteristic Effects of Chemical Force. — It has 
been stated that physical changes alter only the external 
condition of bodies, but do not affect their nature. Chem- 
ical force goes deeper, replacing the distinctive qualities 
of substances with new ones. New properties in the bodies 
formed are the consequence of all chemical action. It 
may convert two solids into a liquid. Thus, when black 
charcoal and yellow sulphur combine, the compound 
formed is colorless as water, and highly volatile. It may 
convert two liquids into a solid, or even two gases into a 
solid, as when hydrochloric acid and ammonia gases unite 
to form ammonium chloride. Sulphur and quicksilver 
unite to form the bright-red vermilion. Nitrogen and 
oxygen are neutral and tasteless, separate or mixed ; yet 



CHEMICAL a« l ; 
of their compounds, lan-lr. , produ< 

delirium when breathed; and another, nitric acid, is an 

i ii t . Mihl and scentless hy- 

and nitrogen form the pungent ammonia; while 
_ and poiaonona chlorine gas, united with ■ brill- 
iant m ommon Bait Then 
however, a gradation in these i - si- 
bling each other lose only part of their properties; but 
th • wider their differences the more complete is the brans- 
formation. Thus, sulphur and selenium are similar sub- 
I compounds of the two resemble their oon- 
tnents; bat snlphar is very nnlike copper, and a com- 
pound of these two is very different from either. 

129. Gradations in Chemical Attraction. — When 
bodies anil m i nei . the chemical force 
may n- l, and tin* compound may again unite 

b other substances, forming bodies still more complex. 

h cases the combining power is pn rely 

weakened. Sence highly complex b •• generally 

less than simpler mirs. Thus, for example, «rwal- 

liaed alum, a complex substance, may be easily decom- 
posed r ampler compounds, water and barn! alum. 
. again, may rated into potassium ral- 
ind aluminum sulphate. But it requires greatly 

reased power to decompose tlioc into sulphur, p<»ti 
Uid aluminum. 

130. Conditions of Chemical Action. While a m 

or a ray <>f light, will cause Borne elements to unite 
tnpounds, and will break up certain com] ato 

. in other cases, SO - «-an he cuinhi: 

ised only by the prol 

the fon which 

• nly ind lit in- 

sults. Thus, while ill 

r into iu gaseoi 



66 CHEMICAL PRINCIPLES. 

hydrogen, these gases can be reunited by passing an in- 
stantaneous electrical discharge through the mixture. 

131. Influence of Heat, Light, and Electricity. — The 
chief way in which heat aids chemical changes is by over- 
coming cohesion, which tends to hold the particles of a 
substance together. Only in a few instances do solids 
combine with solids ; and they unite much more easily if 
powdered or dissolved. Usually one at least of the com- 
bining substances must be in the liquid or the gaseous 
state before chemical union can take place. The effect of 
heat in melting or vaporizing a substance is to loosen or 
destroy the coherence of its particles, and thus make them 
more accessible to contact and combination with the par- 
ticles of another substance. An increase of temperature 
will break the chemical attachments between particles in 
compounds, and it is believed that all compounds can be 
decomposed by a sufficiently high heat. (For the chemi- 
cal action of light and electricity, see Chapters V and VI.) 

132. Catalysis. — This name is given to the remarkable 
power of certain substances to cause chemical changes in 
others simply by their presence, and without undergoing 
any change themselves. The best-known example of these 
catalytic or contact substances is finely divided platinum 
(called platinum-sponge or platinum-black), in the pres- 
ence of which oxygen and hydrogen combine at ordinary 
temperatures, forming water. This platinum-sponge con- 
denses gases on its surface, and is supposed to give their 
particles increased motion, and thereby to induce combi- 
nation. The action of some catalytic substances seems to 
differ from that of others, and has not yet been sufficiently 
cleared up. 

133. The Nascent State. — Substances just liberated 
from union with each other are said to be in the nascent 
(forming) state ; and, at this moment, they often enter 
into combinations which could not be found under other 
circumstances. Nitrogen and hydrogen gases, if mingled, 






[NTKN8IT1B9 OF CHEMICAl ACTION, ,;; 

not anite; but when Bel free from their oombinati< 
they readily combine with each other at the momenl of 
mica] change, to form ammonia. 

134. Intensities of Chemical Action. Chemical t 

J\ an infinite r intensity. Sometiti 

the clou rooeed dowly, as in rocks and soils; Bome- 

tin, ; growth, d iction : and 

sometimes with great violence, as in combustions and i 
plus Our lives depend upon that quiet rateofohemi- 

eal change which takes place in breathing, digestion, and 
-si-s within our bodies. But chemical foroe 
may act with Bach terrific power that a few ounoee of 
nitr ploded upon the surface of a rock will 

itter it I That we are able to use Bnoh a 

e and control its operation 
inflexible Ian s. 

135. The Mathematical Basis of Chemistry. One of 
the greatest modern times is the truth that 

tare works with the -an. on the Bmall Bcale 

as on the large. It is the glory of Newton to have proved 
that the materia] objects of the universe attract each other 
mathematical law by which all the 
and terrestrial motion- of bodice are regnla 
It \ established by chemists thai the minutest par- 

ticles of matter, in their actions and ret 
responding law, and th chemical compound ha 

• itation i .it of the solar - 

If. Th ■ h our feet, and the 

v-es of niat- 

hroughout their inni nstita- 

the harmony of nun fuel we hum ua.-trs 

aw a and passes beyond the 

rea< _dit ; but the invisible <•'• in- 

seen particles are defii ind harmonious, 

so it is with all chemical mutation 
fling had att 



68 CHEMICAL PRINCIPLES. 

that, however often matter might change its form, nothing 
was either gained or lost — that its quantity remained the 
same ; and it was soon found that the constituents of chemi- 
cal compounds always combine in the same proportions. 

136. The Law of Definite Proportions. — We can pour 
alcohol into any quantity of water, and the two liquids 
will mix uniformly. We can melt one pound of zinc with 
two, three, or four pounds of copper, or in any other pro- 
portion, and make a brass or alloy in which the two metals 
will be uniformly mingled. But when substances com- 
bine to form a chemical compound, a certain quantity of 
one always unites with a certain quantity of another. If 
there is more than the right proportion of one, part will 
be left over, and can be separated from the compound 
unchanged. When sodium and chlorine are allowed to 
combine, 23 parts by weight of sodium always take up 
35*5 parts of chlorine, the compound being common salt. 
Caustic soda always consists of 1 part of hydrogen to 
16 parts of oxygen and 23 of sodium. This principle is 
known as the law of definite proportions. The number 
standing for the proportion of an element that enters into 
compounds is known as its combining number. The prin- 
ciple holds, moreover, in the union of compounds with 
each other, as .well as with elements ; the combining num- 
ber of a compound being the sum of the combining num- 
bers of its constituents. 

137. The Law of Multiple Proportions. — It has also 
been found that two elements may combine so as to pro- 
duce several different substances, and that the proportions 
of one or both elements will be different in the different 
compounds. But these differences are in simple numeri- 
cal proportion, the quantity of one or both elements being 
exactly two, three, or more times its combining weight. 
Hence, when combinations occur in more proportions 
than one, the larger quantities are multiples of the smaller 
by a tvhole number. This principle is called the law of 



Tin: atomic THEORY 

multiple proportions, and is illustrated by the following 
iple of the ratios in which carbon and oxygen unite: 

( .: 16 

Th' of the law is still better Been in the i 

mpounds of nitrogen and oxygen : 

\ ' ■ I \ i, 1 1 OlJ ■- :i. B 

Ni; '11 1«". 

Ni:- M 11 M M 

Nitr..-. • M 11 

Ni: M 11 '• 10 

138. Equivalent Proportions. — 1 1 results, from the fore- 
g, that the proportions, or multiples of them, in which 
tmbine with a third, are those in which they 
ine with each other. For example, 3 1 parte of chlo- 
rine unite with 32 parts of sulphur, and with 56 pari 

is the ratio in which sulphur 
combines with iron. These relative numbers hav< 
[uivalenl proportions, or equivalents. 



CHAPTEB IV 

THEORETIC LI I HEM 181 SI , 

139. The Old Atomic Theory. — It was an ancient 
latinii thai all matter is made up oeedingly 

minute particles, which I with qualil 

•i which depend the pro] d the 

effect 
these particles an ibdivided 

this 



70 CHEMICAL PRINCIPLES. 

question, and the vague notion of the atomic constitution 
of matter remained for thousands of years nothing more 
than an ingenious guess. 

140. Its Reappearance. — But, when science had ex- 
perimentally proved that there are definite numerical 
relations among the minutest parts of matter, this old 
problem was placed in a new light. The idea of the 
definite proportions of chemical combination, at first 
strongly resisted, was established near the close of the last 
century. It was soon extended by Dr. Dalton, of Man- 
chester, England, who discovered the law of multiple pro- 
portions ; and, to explain it, he went back to the old Greek 
idea of atoms. He assumed — 1. That all matter consists 
of ultimate and unchangeable particles or atoms ; 2. That 
atoms of the same element have a uniform weight, but 
that in different elements they have different weights; 
3. That the combining numbers of chemistry represent 
these relative weights ; and, 4. That between these differ- 
ent atoms there are attractions which unite them into 
chemical compounds. Dr. Dalton maintained that, if 
these ideas are accepted, the constancy of chemical char- 
acters and the definite and multiple proportions of com- 
bination follow as necessary consequences. This theory 
has been of great service in the development of the science ; 
but it has been gradually much altered and extended. 

141. The Molecule in Physics. — This development of 
the atomic theory has consisted in the far greater promi- 
nence and distinctness now given to the conception of the 
molecule — a conception which has become fundamental 
both in physics and chemistry. We have seen (24, 25, 27) 
that the physicist regards all matter as made up of sepa- 
rated units, with intervening spaces that allow more or less 
freedom of movement ; and that, in this way, he accounts 
for the phenomena which belong to the three states of 
matter. To the physicist, therefore, molecules are not 
abstractions, but actual things, having definite sizes (179), 



THE KOLB01 71 

and he defines them m 
which pass without alt 

>d by (/< 

142. The Molecule in Chemistry. -To the chemist the 
molecule has al> am im lrss a lval tiling, l»ul hr \ i< 

it in a ililTen nt aspect. The physicist tali a unit, 

to what ii is made of ; hut this 

. what the chemist wishes to know. Be is to find 

■ whether the molecule is simple or compound, what 

kind or kinds of matter it contains, and how it is built up. 

for example, grinds a bit of sugar down to 

the finest particles of microscopic dust not the ten-thou- 

iU inch in diameter, but each particle still p 

I the pi a of the lump, and he is ?ery Ear 

from h rrived at the molecule. II«' now puts 

it into water and it disappears. The risible particle may 

thus divided into perhaps millions of molecules, and 

when the * ed the sugar rea with all 

1. Again, a bit of common 
into va|»<»r, its molecules 
driven widely apart, but when 

the substance, with its character unaltered. The chemist 

from his point of new. II<' beats it, or 

acts upon it trong chemical agent, and finds that it 

gen, and hyd] 

1, and the three new sul - 
d from qua] it in weight The 

chemically a unit, 
compound. !! that tl 

ind also, of two different kinds of i 

lium. T 

till simpler 
units; so h< 

143. The Atom in Chemistry 1 he ultimate unit of 



72 CHEMICAL PRINCIPLES. 

the chemist is the atom. Molecules and atoms, in the 
present state of chemical science, represent totally differ- 
ent things. A molecule is a group of atoms united by 
chemical affinity, and capable of existing by itself; an 
atom is the smallest quantity of a substance that can enter 
into combination to produce the molecule. Atoms are in- 
destructible, molecules are susceptible of endless change. 
A group of the same kind of atoms forms an elemental 
molecule; a group of different kinds of atoms forms a 
compound molecule. 

144. Symbols of Atoms. — The chemical elements are 
represented by symbols which are generally the first letters 
of their names or of their Latin synonyms, and where dif- 
ferent elements have the same initial letter a small letter 
is added. Thus, N stands for nitrogen, B for boron, Br 
for bromine, and Fe for iron (ferrum). 

But the letter does not merely represent the substance ; 
it stands for a certain quantity of it, the smallest that can 
enter into combination — the atom. H not only symbolizes 
hydrogen, but one atom of it, the weight of which is taken 
as 1. C stands for the carbon-atom, which has a combin- 
ing weight of 12 ; and for the oxygen-atom, weighing 
16. These are the proportional numbers of combination, 
and are also called atomic numbers. The molecules will, 
therefore, be represented by writing together the symbols 
of the atoms of which they consist, thus : H, hydrogen, 
and CI, chlorine, combine to form hydrochloric acid, HC1, 
the symbol of the molecule. The single letter always sig- 
nifies one atom, but, if several atoms are to be indicated, 
small Arabic numerals are employed, thus : S 6 means six 
atoms of sulphur, P 4 , four atoms of phosphorus ; H 2 rep- 
resents the molecule of water, consisting of two atoms of 
hydrogen with one of oxygen, and C0 2 , the molecule of 
carbon dioxide. To represent several molecules a large 
figure is prefixed, for instance : 2H 2 indicates two mole- 
cules of water ; 4C0 2 , four molecules of carbon dioxide ; 



PRO CHEMICAL THBORI 

0, ten molecules of iloohoL H\ adding to 
the atomic weights of the elementa in a molecule 
molecular weight* Thus, for water (H«0) f it is 
(H) 1 + (H) 1+ (O) L6 L8; tor carbon dioxid* 

it ia (C) 12 -r I • (O) L6 n n. The symbols and 

mio nini all the elementa arc given in a table in 

the Appendix 

Theory. 

145. Earlier Views. -The present state of the BcieiMX 

ry lias been reached by a gradual progress from 

vaj: ma to more and more intelligent theories, made 

by an ever-widening knowledge of facts. The 

•it theories of material things supposed them 

all to b ue one Bubstance as air, water, 

tire — which was assumed to take many different forms. 

oombinetL The objects of nature 

we- formed of various mixtures of four ele- 

menta -fire, air, earth, and water; and for many centuries 

ties an 1 ehai .ill Bubstances, animate and 

inanimate, were explained on this hypothesis. In the 

sev. ighteentih centuries, alchemy, the old 

: of the art «.f gold-making, gradually grew 

ienoe of experiment by which much became 

known of the qualities of different kinds of matter. I >ur- 

entfa century chemical chs 

theory of phlogiston. This was held to 

t kind <>f subtile matter, present in all combustible 

absent in all ii. i which 

C^C.ljM'. Til." d< 

(1 as a ide one, but it 

ind wm me. With the 

"<Hlucti<>n of the balaie « hemical nseandi, the 

tfa by which it llv 

advancH for i hundred years. The use of | 

m the d 

4 



74 CHEMICAL PRINCIPLES. 

those laws which constitute the theoretical chemistry of 
to-day. 

146. The Binary Theory; Dualism. — With the aban- 
donment of phlogiston as a ruling principle of chemical 
change the conception of affinity came forward, and chem- 
ical effects began to be referred to inherent attractions 
among different kinds of matter. At the time of La- 
voisier, affinity was thought of simply as a coupling force. 
Combination and decomposition were supposed to take 
place directly among bodies in pairs; elements uniting 
with elements to form binary compounds, and these unit- 
ing again by twos to form double binary or ternary com- 
pounds ; and, when these were made to exchange one con- 
stituent, the reaction was represented as a double decom- 
position. This was known as the dual theory. Powerful 
support was subsequently lent to it by electro-chemistry. 
Compounds were resolved into pairs by galvanic action, 
and their elements were supposed to be in opposite elec- 
trical states, and to be united by polar forces. 

147. Substitution Theory. — But, as chemical changes 
were more closely studied, it was increasingly felt that the 
binary theory gave a very insufficient account of them. It 
was found that the changes which take place among 
chemical compounds were rather of the nature of replace- 
ments and substitutions, which left the structure of the 
molecule intact. The molecule gradually came to be re- 
garded as a group of two, three, or more atoms, instead of 
as made up always of two atoms or two pairs of atoms. 
The constitution of the molecule, therefore, became the 
main object of investigation. It was found, moreover, 
that the most opposite elements could replace each other 
in a group without altering its chemical character. Chlo- 
rine, a powerful electro-negative element, could be substi- 
tuted for hydrogen, a strong electro-positive element, in a 
compound, without changing its characteristic properties. 
Groups of atoms, moreover, such as cyanogen (CN), am- 



AFHMinTY AM' ulAYriYAl.KV 1 ;;, 

'i in in ( N 11 ; ), ethyl (( 1 1, ), and many more, Were found 

bo w ■: as substitutes for elements in oompounda SucB 

L r ra<luall\ 1 tin* binary <>r electro-chemical 

ive way to the doctrine of substitutions. This 

doctrine considered Baits uo( as binar] compounds of acid 

. at as prodi substitution from acids, in 

icb hydrogen had been replaced by some other element. 

The formal mmoo Ball was no longer NaO + Ilcl, 

but NaCl, signifying hydrogen chloride, in which hydro- 

d substituted by Bodium | Na ». 

148. Theory of Chemical Types. The substitution 
theory attained fuller expression in the theory of ty] 

in which molecular structure first became a basis of classi- 
:i«»n. Most chemical changes were viewed as replaoe- 
. which conformed to a tew general modes. A- the 
8toi. :i edifice may be successively exchanged, leav- 

ing the style of architecture undisturbed, bo atoms may 
re] . leaving the types of molecular structure 

ui!;. This important idea was at the basis of the 

theory. Gerhard! proposed tour Buch general types or 
Jung hydrogen, hydric chloride, water, and 
tentative bodies, and classing with them 
all snl. dibit analogous reactions. Bui the 

• t i .- 1 1 oompoii n- ><> numerous that the 3] stem 

wa« held to be inadequate for classification, though in- 
to somel bing broader and 

re satisf;. 

149. Variable Combining Capacry 

ol chemical combination now adopted is th owth <»f 

-. but it adds an important principle 
main. Under the binary I 
wa~- men! always on 

ment When t ; itu- 

it the replace- 



76 CHEMICAL PRINCIPLES. 

ments were atom for atom. But it is now recognized 
that, while certain kinds of atoms interchange with each 
other as true equivalents, atom for atom, it is found that 
in other cases it takes two, three, or half a dozen atoms of 
one kind to equal one of another kind in combining power. 
The idea of variable combining capacity of atoms and 
molecules has been worked out with great clearness, and 
is the distinctive feature of what is now known as the New 
Chemistry. 

150. Atomicity. — To determine these degrees of equiva- 
lence of different bodies, we have but to take some one, 
which will serve as a measure of comparison between them. 
Hydrogen answers this purpose. It unites with chlorine, 
atom to atom, forming the molecule of hydrochloric acid, 
HC1 ; but oxygen can not combine with hydrogen in this 
way ; it must take two hydrogen atoms, forming the mole- 
cule of water, H 2 0. Nitrogen again takes three atoms of 
hydrogen, forming the molecule of ammonia, H 3 N ; and 
carbon behaves still differently, demanding four hydrogen 
atoms, as in the molecule of marsh-gas, H 4 C. We have, 
therefore, the four following molecular constructions : 

HC1 H 2 H 3 N H 4 C 

Hydrochloric Acid. Water. Ammonia. Marsh-Gas. 

which vary in a regular numerical order. This might 
seem to be accidental, but it is not so, for, if we take 
chlorine instead of hydrogen as a measure, we shall get 
similar results, as follows : 

NaCl HgCl 2 SbCl 3 CC1 4 PC1 5 

Sodium Mercuric Antimonious Carbon Phosphoric 

Chloride. Chloride. Chloride. Tetra-chloride. Chloride. 

Now this is not something that merely happens among 
a few selected substances ; it illustrates a law that has 
been traced through the relations of all the elements. It 
is obvious that in the first four groupings the elements 
chlorine, oxygen, nitrogen, and carbon can no longer be 



EXPRESSION i wtiv.m.kv 77 

led as equivalents Ol ftacli other ; nor arc the sodium, 

nry, antimony, carbon, and phosphorus of the second 
group equivalents *>\' each other. Each element seems t<> 

its own atomic capacity. Hydrogen, sodium, ami 

chlorine [ iherin one-; OXygeu ami mercury take 

hydrogen ami chlorine by twos ; nitrogen ami antimony 

take them by three-; carbon takes both by fours; and 
phosphorus takes its chlorine in ti\< 

151. ftuantivalence and its Expressions. -To these 
chemical relations the general term quantivalence, or 
, has been applied ; and different modes are em- 
d to indicate the several valencies <»f the different 

elements. They are as follows: Bodies wh<»e atomic 

Two " I > . Kb, " 8 9 U nt. 

Three u mt 

Foir 

y\\,- M Prntocb, M Q 

H 

Ododty .'.nt. 

Bodies with a higher atomic capacity than one are 
to be multivalent. Bydrogen, in the single compound 

it forms with chlorine, is assumed as the standard of 
quantivalt I Valency is also expressed h\ 

(olio 



II' 



I»va-!s 



Tri.i.ls 

V" 
B 



T'-trr\.N 

I 



F 






w- 



With d the indices of atomicitj . rally as- 

• 1 and not wrir 

152. Bonds. -To illust learly the bk 

and Die of theM indi< hemi<al 

lines, as 



78 CHEMICAL PRINCIPLES. 

Monad. Dyad. Triad. Tetrad. Pentad. Hexad. 

H- -O- V -C- >P< >Fe< 

These links or dashes are termed bonds. When chem- 
ical affinity takes effect, it is assumed that the bonds of 
different atoms are joined together, and they are said to 
be satisfied, or closed ; when not so joined they are unsat- 
isfied, or free. The previous examples, in which numerals 
were used, would be represented as follows by the use of 

bonds : 

H 

H H-C-H 

H-Cl H-O-H H-N-H H 

Hydrochloric Acid. Water. Ammonia. Marsh-Gas. 

ci C1 

Cl Cl-C-Cl C1 \^/ 01 

Na-Cl Cl-Hg-Cl Cl-Sb-Cl Cl G\ \\ 

Sodium Mercuric Antimonious Carbon Phosphoric 

Chloride. Chloride. Chloride. Tetra-chloride. Chloride. 

153. The Bonds control Combination. — We have here a 
controlling and limiting principle of all chemical changes. 
In every combination each bond requires to be satisfied, 
and an atom can link itself to others only to the extent of 
its bonds. Only those elements can unite with each other, 
atom to atom, w T hich have the same number of bonds. 
The atom of chlorine has only one bond, and hence can 
unite with one atom of hydrogen or sodium, each of which 
has also one bond. The oxygen atom has two bonds, and 
hence can combine with two atoms of hydrogen, giving 
one bond to each. An atom of mercury has also two 
bonds, and while it can take up two atoms of an element 
like chlorine, it can combine with only one atom of oxy- 
gen, for both bonds of one must be used to satisfy the two 
bonds of the other. If an atom has four or five bonds, it 
may make a variety of combinations; thus, phosphorus 
may hold five atoms of chlorine, or three atoms of chlorine 
and one of oxygen. On this theory, we view every chem- 



VARYING QUANTIVALKS 

ical oompound aa a molecule irhicfa can exii atelj in 

the balance ol all its attractions, as shown 
losing of the bonds «>f all its atoms. 
154. Varying Quantivalence in the Same Element 
re n<>t limited to one d< qoantivateii 

may act eiti triad or a pentad ; iron 

:i-l, or 1'. I <>t* the other ele- 

different quantivalent relations. I' 
remarkable that tin- Bame element in changing it- quan- 
chemical relations almost as if it 
bee • u elem< ompounds with other elem< 

being widely differ rding to its different Btates of 

\. Thus, triatomic nitrogen in ammonia, and 



11 


11 


.1 N 


1 n a 


II 


11 .i 




Ajnmooium Chloride. 



mic nitrogen in ammonium chloride, L r i\e rise to 

compounds, with a marked difference of 

pn But the replacing and atom-fixing power of 

i wery unequaL Tl 
sulphur . and lead asa tetrad; but both are 

tmmonly dyads. N is a pentad, but much 

Bodies have thus a higher and 
ed to apply the 
to t he b •• that the] evef 

important property of an i 
he leadii iling quantn 

is al ases or dimini-l >\ n. 

II- 111 n<|f] 

thr ir, ami 

whose quantn 



80 CHEMICAL PRINCIPLES. 

155. Theory of Change by Pairs. — When an atom uses 
less than its whole number of bonds in combination with 
other atoms, it is believed that the remaining bonds satisfy 
each other by twos. The fact that a single bond is never 
suppressed is thus accounted for, and a reason given why 
artiads and perissads are inconvertible. As the bonds can 
only be saturated in pairs, a pentad can become a triad 
and a monad successively ; and a hexad may be converted 
into a tetrad or a dyad, as follows : 

Perissads. Artiads. 



Pentad. Triad. Monad. Hexad. Tetrad. Dyad. 

r> £» -0 # & & 

156. The Free State of Elements. — As an atom or a 
molecule can exist separately only when its bonds are all 
closed, that is, when its quantivalence is satisfied, it fol- 
lows that atoms of elements with odd quantivalence 
can not exist free. The odd bond must be satisfied. 
In hydrogen gas, therefore, the condition is not atomic, 
as H-is impossible; but it is molecular, or H-H. So 
in free chlorine (CI - CI) and sodium (Na - Na) the 
atoms are paired to form molecules. As the even bonds 
of the artiads can close each other, these elements 
may exist as separate atoms ; oxygen being either = 
or >. 

157. Importance of Mode of Linking. — The quantiva- 
lence of a molecule does not depend entirely upon that of 
its elements, but partly upon the manner in which they 
are united. When multivalent atoms are connected only 
by single bonds, the remaining bonds will be free, and de- 
termine the quantivalence of the group. Thus, the mole- 
cule C 2 H 4 may be either satisfied or diatomic, accordingly 
as two bonds of the carbon atoms are disposed of. This 
is seen by comparing the following symbols : 



M'KI- jl l;i; OK MOI.iyi [J> 81 

II T B " ? " 

.. 1 " ( " 

SaiiMi.M. i in. 

158. Structure of Molecules. — < )n this view it ifl impos- 
• avoid the idea of the great importance of the 
grouping of atoms in molecules. If the relations among 
Midi that they can be most accurately repre- 
sent tie mechanical conception of bonds and clamps, 
thai turr in the molecules inevitably follows. These 
>tructi t ' of different orders. With monads we can 
only get molecules of the simplest construction, in which 
the paired, as K -('1,11 -I. As & monad lias 
hut one bond, it can never join ether atoms together ; hut, 
wh' introduced, the molecular structure becon 

The dyad performs a linking function, and 

in union with monads {>ro<lucr> molecular chain.-. Oxyj 
vrlv in this way. as in 

H-0 -H H-0 Oi II 

Quotum U\> irate. 

an«l, by introducing moi in links, such chains maybe 

indefinitely extended With atoms of higher quantint- 
len omplexity is increased in a still greater degn 

the multivalent atom pbying the pari of a nucleus. The 

following seli.-rne r- •> the « onstitution of common 

alum as a saturated moleoul 



S 
« » « » o 

K - \l A I - <> I 

6 b 6 ft 



oo 



82 CHEMICAL PRINCIPLES. 

The double atom of aluminum is the nucleus of the 
group, and combines four subordinate groups, each having 
a nucleus of hexadic sulphur. It matters nothing how 
such a scheme is drawn, so that the atomicities are all 
satisfied, but from the way such complex molecules break 
up in decomposition we can infer something about the 
definite order of arrangement among the atoms. 

§ 4. Theory of Radicals. 

159. Simple Radicals. — The term radical has long been 
applied to any chemical body which is considered as the 
essential ingredient, or basis of a series of compounds. 
Thus, potassium, sulphur, and, in fact, any element may 
be taken as the starting-point or root of such a series. 
The simple radicals or elements are generally divided into 
two great classes, which differ widely in chemical proper- 
ties — the metals and the non-metals. The former, being 
electro-positive, are called positive radicals, while the oth~ 
ers are electro-negative, and are called negative radicals. 

160. Compound Radicals. — But it has been established 
that there are groups of elements so bound together that 
they play the part of simple bodies, and are therefore called 
compound radicals ; thus, carbon and nitrogen combine to 
form the radical cyanogen (CN), which is the root of a 
series of compounds much resembling those formed by 
chlorine. Ammonium (NH 4 ) is a compound radical, 
which behaves in chemical reactions closely like certain 
metals, combining with chlorine, sulphur, and cyanogen. 
Methyl (CH 3 ) is the radical of methylic alcohol; and 
ethyl (C 2 H 5 ) is the root of ethylic alcohol, both of which 
are traceable through numerous affiliated compounds. 

161. Quantivalence of Compound Radicals. — Compound 
radicals also obey the laws of quantivalence like simple 
radicals. In general they can not be isolated, as they are 
unbalanced molecules ; but some of them pair with each 
other like elementary atoms, forming saturated molecules 






\<ll>s AM' BASES 

[oh can « its The radical hydroxyl, 11 1 1 , 

can not, as it unsaturated bond, i e, but) 

ipled as 11 - < > - n - 11, it forma the compound known 

as hydrogen di< Che compound radicals interchange 

.1 with the Bimple radicals, under the 

usual limitations ling to the number 

ta re] i by the graphic Bymfa 

the foil - Qonatomi 

ii H ii li n 

\ ii ( n-( i 

H n ii ii ii 

An yl. Kthvl. 

162. The Old View. — These numerous and important 

explained in a vm simple waj on 
dual theory already noticed (146). I id and 

base wa> supposed to be a binary compound consisting of 
■ metal un al, and a Ball was belie ■ 

e joined to 
opounds or double Baits a 
known, whioh were thought to be formed by the union of 

163. Constitution of Acids. The best-known oharao- 

lolution 

of a id in wi mon-juiee oontai ■■i<l, 

milk turns .-our b ilso 

in- 
stance, blu< : bu< th( ible 

table col 

form tin* larger class, and 

I I II. 

•I).' 



86 CHEMICAL PRINCIPLES. 

2H-01 + Na-Na = 2Na-Cl + H-H 

Hydrochloric Sodium. Sodium Chloride 
Acid. or Common Salt. 

+ - + - 

Salts of both the types R - - E and R - R are normal 
salts. They contain no hydrogen and possess neither acid 
nor basic properties. Hence they are also called neutral 
salts, and an acid and a base are said to neutralize each 
other when they unite to form such a salt. 

166. Basicity of Acids. — In the examples given in 163 
the radicals are all univalent, but multivalent radicals may 
form acids also. In such cases the radical must be re- 
garded as replacing a hydrogen atom in two or more 
molecules of water. 



Si 







H-O^ 






H-O) 


H-0 




1:8} (s°.) 


H-Of(PO) 
H-O) 


H-0 
H-0 


> 


Sulphuric Acid. 


Phosphoric Acid. 


Silicic Acid 



The hydrogen in an acid, which can be replaced by a posi- 
tive radical when the acid is brought in contact with a 
base, is called basic hydrogen. An acid like nitric or hy- 
drochloric which has one replaceable atom of hydrogen 
is called monobasic ; sulphuric acid is dibasic, phosphoric 
acid is tribasic, and silicic acid is tetrabasic. 

167. Quantivalence of Bases. — In like manner bases 
may contain multivalent positive radicals. 

Cal°- H Bal°- H 

^ a |0-H ^JO-H 

Calcium Hydrate. Barium Hydrate. 

The hydrogen in a base which can be displaced by a nega- 
tive or acid radical is called acid hydrogen. A base con- 
taining one atom of acid hydrogen is called a monacid 
base ; one containing two atoms is called diacid, and so on. 

168. Classes of Salts. — In a polybasic acid sometimes 
only part of the displaceable hydrogen is replaced by 



OXIDBa v; 

ids, and a salt retaining a partly acid character and 
called an acid Ball ifl formed ; for install 

11 u . ' 
I Bodkm Sulpha) 

metallic radicals may each replace part of 
the 1. in an acid molecule, a> in NaKCOi (sodium 

169. Water of Crystallization and of Constitution. — 

separating from solution in water form 
one or more molecules ot vrater for 

the sail. Water thufl unite 1 with Baits 

itallization, for, when it is driven oflf, 

>rm can no longer be retained, and the 

ot white or colored powder. 

Whei rials of magneeinm sulphate, which have the 

formula M _^ ( >.. 7H t O,are heated to LOO 0.,six molecules 

of tral T. and I bance falls to powder. 

rtalliaation. The 
me remaining molecule is united more closely with the 
sulphate than these are; it is only driven ofl by a tem- 

of 210 . and i f can be replaced by a molecu 
another sulphate, jusl as if it were s constituent part of 
sompoui . □ M _ v( ►.. K ^< >.. • I In. 

: with a sail ifl called wati 

170. Oxides. — Oomponnds of oxygen with a mi 

If the radical is i , the 

i i- call* or anhyd 

1 i anhyd] without i 

P.O, + H u aHPO 

;i poeiti 
is called HfO 

. a base is formed 



88 CHEMICAL PRINCIPLES. 

Na 2 + H 2 = 2NaOH 

Sodium Oxide. Water. Sodium Hydrate. 

Some oxides are neither decidedly basic nor decidedly- 
acidic, but have a little of both characters. 

§ 6. Theory of Isomerism and Allotropism. 

171. Inorganic Chemistry in Relation to Theory. — 

Chemical science has been long divided into two great 
branches — inorganic chemistry, which treats of non-living 
or mineral substances ; and organic chemistry, which treats 
of matter that composes the parts of organized bodies, vege- 
table and animal. In the former department the chemist 
deals with all the elements of nature in their simple com- 
binations ; in the latter he is occupied with only a very 
few elements, but these unite to produce great numbers 
of complex substances whose obscure chemical reactions 
make their study difficult. In fact, organic chemistry was 
long regarded as an impossibility, under the belief that 
the vital force dominates in the organic sphere, and sus- 
pends the ordinary laws of chemical action. It was there- 
fore natural, and indeed inevitable, that inorganic chemis- 
try should be cultivated first, and that the earlier theories 
of the science should be framed upon the knowledge ob- 
tained by studying the simpler and more general phe- 
nomena. Yet the domain was partial, and the knowledge 
limited ; for organic chemistry was a legitimate and most 
important division of the science, and its numerous and 
remarkable facts being left out, the prevailing theories 
were necessarily defective. 

172. Organic Chemistry in Relation to Theory. — But it 
was impossible to confine the chemists within these early 
and arbitrary limits ; they pressed into the organic field 
and were rewarded by the discovery of multitudes of new 
substances, many of them of great importance. They also 
made an unexpected conquest by forming, artificially, va- 
rious compounds which had hitherto been regarded as 



Tin: ORGANIC BLBMBN I gg 

ible only under the inflnenoe of life. Much u 
unity was $i first employed in trying to bring the new 
beta into harmony with pre-existing theoretical news. 
These efforts, however, proved futile. A uew ohemistry 
sng up in the new province, which, instead of being 
subordinated to old theories, greatly modified them. Thus, 
fn»m a neglected region, long supposed to lie beyond the 
bounds of the science, there came an influence thai has 
changed its whole theoretical character. The modern 
tie distinctive of the nei system changes by 

ition, typep, unitary groups, atomicity, and the con- 
trolling importance of molecular structure have all arisen 
through the modern investigation of organic Bubstan 

173. The Organic Elements. -Four Bubstanoei make 
up the main hulk of organised bodies throughoul the en- 
tin ie ami animal kingdoms, I i/... hydrogen, oxygen, 

nitrogen, and carbon. The three first named an 

solid, which has never yet heen melted, or \ola- 

tilized. B] its multivalence carbon is enabled to combine 
with itself in series aft i of radical groups, which 

the nuclei of a countless host of compounds hy 

linking with atoms and groups of other elements. The 

title organic ohemistry is in tad disappearing, and bo im- 

the pari played by carbon thai this division of 

ow known as the ( Ihemistry of the I 'arbon- 

inds. We may, indeed, declare that the number 

of kre.wn compounds of this one element is Car great 

than those of all the oth< 

174. Isomerism. In b tnio substances oom- 
inds "f the most diverse pn e found to oon- 

sist hip' elemenl 

jhc .ndition dytic inquu 

ly (ailed. It was not 
gan. orients and tie- pro] 

■ d. Ch< 
forced to m 



90 CHEMICAL PRINCIPLES. 

in their atomic arrangement. Butyric acid, an oily liquid, 
not easily inflammable, which has the disagreeable smell 
of rancid butter, and gives the acid reaction, has the for- 
mula C 4 H 8 2 ; while acetic ether, a limpid liquid, non- 
acid, easily inflammable, and having the pleasant, fruity 
smell of apples, has also the formula C 4 H 8 2 . These sub- 
stances are therefore said to be isomeric, a term meaning 
composed of the same constituents in the same proportions. 
There is no way of explaining this difference of properties, 
except on the theory that the constituent atoms are differ- 
ently grouped in the two cases. And this is proved by 
acting on the two molecules with chemical agents, when 
they break up in very different ways, and give rise to dif- 
ferent products. Isomeric compounds are often convertible 
into each other without loss or addition ; their different 
properties must therefore be ascribed, not to the presence 
or proportions of certain elements, but to .the influence of 
molecular clustering and structure. Isomeric bodies are 
called isomers. 

175. Kinds of Isomerism. — There are several kinds of 
isomerism. If bodies have the same absolute composition, 
as in the example just given, they are said to be metameric 
compounds. But some substances, which contain the same 
percentages of the same elements, have not the same num- 
ber of atoms of each element in their molecules. One 
contains two, three, or more times as many atoms of each 
constituent as the other. They have only the same pro- 
portions of elements, and are then said to be polymeric 
compounds. Thus, acetylene, C 2 H 2 , and benzene, C 6 H 6 , 
are polymers. 

176. Allotropism. — Closely allied to isomerism, in fact, 
the same thing, only limited to elementary bodies, are the 
phenomena of allotropism, or allotropy. Thus, phos- 
phorus, sulphur, and carbon exist, each in several differ- 
ent states, with totally unlike characters, and called allo- 
tropic forms. It was at first supposed that but few of the 



ATOGADRO'S LAW. «,♦! 

allotropic, bi now found thai a Con- 

di them take on these varied conditions, 
effects hitherto offered in thai 
<»f varying arrangement or number of atoms in the 
molecule. 

g 1 . 

177. Space-Relations of Molecules. It baa been Itated 
that the physicist and the chemist agree in regarding 

as actual tilings, pieces of matter, extremely 

minute, but just a- real as planets and stars are to the 

mer. Thus Eur we have considered them only in 

b t<> weight; but if they have weight they must 

od have dimensions. Something has been 

done toward solving this problem of the Bpace-relations of 

. and physics and chemistry have both oontrib* 

i to the result. 

178. The Law of Avogadro. -When a <rivcn amount of 
s applied to equal quantities of different kinds of 

matter in the Bolid or liquid state, the expansions are nn- 

. . unple, the same amount <»f heat is ap- 

plied to equal volumes of water, alcohol, and ether, they 
I but if these substances averted 

int . and thm the same amount of heat is applied 

another result appears \ the vapors all 

I alike. In tin- i-hamr*' to tin- fin- 

i from each other's attractions, and 

•inninn condition Of mutual njuiUi«.n. In 
this sfeat i-«-s ami both in 

. and in contracting 
und«r the infln > an be th< 

marlcable uni 
sweral . :n 1811, as fol- 

lows : 

pratt* 



92 CHEMICAL PRINCIPLES. 

known as Avogadro's law. It can not be directly proved, 
but is indirectly established by the most convincing evi- 
dence ; and it harmonizes and explains so great a number 
of physical and chemical facts, that it is now accepted by 
both physicists and chemists as a fundamental principle. 

179. Size of Molecules. — That molecules have magni- 
tudes is self-evident, and if the principle is true that equal 
numbers occupy equal spaces, it is inferable that they are 
all of equal size. It may be thought impossible to deter- 
mine what those dimensions are, and certainly it must be 
a problem of great difficulty and doubtful results. Yet the 
ablest physicists are trying to solve it, and claim to have 
already arrived at approximate conclusions that are en- 
titled to reasonable confidence. Great advances have re- 
cently been made in minute measurements. Time is 
measured in millionths of a second, and lines have been 
ruled on glass plates numbering 224,000 to the inch. From 
various researches of exquisite delicacy, among others the 
relations of light to the filmy walls of soap-bubbles, the 
conclusion has been reached that the diameters of gaseous 
molecules will not greatly vary from the ^oo- {o,ooo °f an 
inch. Sir William Thomson, who has been prominent in 
these investigations, says : u If we conceive a sphere of 
water as large as a pea to be magnified to the size of the 
earth, each molecule being magnified to the same extent, 
the magnified structure would be coarser grained than a 
heap of small lead shot, but less coarse grained than a 
heap of cricket-balls." 

180. Chemical Application of Avogadro's Law. — If 
equal measures of two different gases or vapors contain the 
same number of molecules, then we have but to weigh 
these equal volumes to get the relative weight of the mole- 
cules. For example, a cubic inch of oxygen weighs six- 
teen times as much as a cubic inch of hydrogen, under the 
same conditions ; but, if in each cubic inch there is the 
same number of molecules, each molecule of oxygen must 



HOLECULAB WRIGHT. 

timee as much as each molecule of hydro- 
We have thus a simple means of determining the 
lecular weight <>f all bodies that are capable of passing 
i ii i 

181. The Unit of Molecular Weight, [f the hydrogen- 

taken as the standard, then the specific 
ous body compared with it would give 
molecula it. Hut the half I hydrogen 

has been adopted as tin- unit, or l. so that the hydrogen- 
molecule will hare t<> be represented bj 2. This mal 
it i i double the specific gravities <>!' gases in 

or-i molecular weight The volume of tin' 

hydrogen-molecule being represented by 2, as all mole- 
cule - ' he Bame volume, they must al><> be represented 
by 2, \- the molecule of hydrogen weighs 3, the mole- 
cule of oxygen, which i- sixteen times heavier, weig 

\ ity of nitrogen, <<>m- 
pared with hydrogen, is 14; its molecular weight is there- 
ton 

182. Physical Verifications.— Tin- method is of great 
importance in chemical investigations, where molecular 

b ts and formulas are t<» he determined. Anal] 

of elements in n compound. 
It I for example, that water consists of B8 # 89 parts, 

by weight, of oxygen, and 11*11 | hydrogen, hut 

this is onlj . and ma J to 1, or 16 

i thai I ■ 
the • her 9, I , Bui if wafc 

.n«l the vapor weighed, it- density turns ou< to 
mes thai of hydrogen ; and this number multiplii 
.esl8a- tual molecular weight of wafa 

i kindred do 
nun ions <»f physics and chen 

d found 

ta Thai is, the num- 



94 



CHEMICAL PRINCIPLES. 



raise equal weights of iron, copper, and lead, for example, 
through the same number of degrees of temperature, are 
inversely proportional to the atomic weights of these ele- 
ments. Hence the products of the specific heat and the 
atomic weight of all elements are equal. This common 
product is called the atomic heat, and represents the quan- 
tity of heat required to raise the temperature of an atom 
of any substance one degree. Its average value is 6*25. 
Moreover, as Faraday found, the quantities of electricity 
expended in decomposing compounds are found to be also 
in definite relation to the atomic weights of the bodies 
set free. 

183. Combining Volumes. — Gases combine by volume 
in very simple ratios; in some cases in equal measures 
without condensation ; but if condensation occurs it is by 
whole units, as 2 volumes condense to 1, 3 to 2, or 5 to 2, 
as illustrated in the following cases : 



+ 



Hydrogen. Chlorine. 



Hydrochloric 
Acid. 









+ 






Hydrogen. 



Carbon. 



Water. 



Ammonia. 



_L 



Marsh-Gas. 



MBINING V0L1 UBS 9fi 

184. Theory of these Effects. -The Foregoing I 

volume are simple resul tperiment; hut, 

if A - assunu'il that cpial teas-volumes OOn- 

tain equal uumbera of molecules, the theory of quan- 
tivalence explains the effects. In the first case, we have 
- in diatomic molecules 11 II and Cl-< 
i equal volumes contain an equal number of these m< 
rules. When the ; mingled, the molecules inter- 

atoms, producing B-Cl and II -CI, luu, as the 
number of molecules remains tin- Bame, the volumes re- 
main unaltered. In the Beoond case ire have the dyad 
, the molecule of which is (M). Each of its atoms 
link- two of hydrogen, forming the triatomic molecule 
II. 0« The total number of molecules is thus diminished 
a third, and the three volumes are consequent^ redu( 

In the third example we have triadic nitrogen, 

the molecule of which is \A. Bach nitrogen-atom 

gen-atoms, forming ammonia, 1 1 N. All 

the molecules at first contain two atoms, and the resulting 

xmtain four. There is, thei >u1 half the 

number <»f molecules, and the four volume- an- iv<lu<v<l 

h atom <>f the tetrad carbon molecule, 
with four atoms of monadic hydrogen, and 
the resulting molecule contains five atoms. The num 
of molecules formed equals the number of carbon 
or ti i( krbon-moleoules, and b< 

condensed to I ^ ( »- 



OHAPTEB X. 

ATOXIC WEIGHTS wi> THE PROPERTIES Of I I i m :• 

185. Classification of Elements.— It wn 
impoasil age the in a 

natural system. ] 



96 CHEMICAL PRINCIPLES. 

rating those of unlike characters. Although we have not 
yet arrived at a satisfactory classification, modern research 
has furnished results which enable us to replace the im- 
perfect earlier systems with one which more accurately 
represents the existing state of the science. After New- 
lands, in 1866, had pointed out the essential importance 
of atomic weight and its intrinsic relations to all other 
properties of the elements — physical as well as chemical — 
Mendelejeff and Lothar Meyer, about 1870, separately suc- 
ceeded in establishing what is known as the periodic laiv. 
186. The Periodic Law. — Omitting hydrogen for the 
present, if we examine the next seven elements in the 
order of their atomic weights, we shall find that the sec- 
ond differs in character from the first ; the third differs in 
the same way, but still more, from the first ; the fourth is 
still further different in the same direction, and so on, 
until the seventh is reached. Lithium (atomic weight 7) 
is the first element in this series. It is very easily oxid- 
ized, forming an oxide of the type R 2 — i. e., two atoms 
of this element unite with one of oxygen. The oxide is 
strongly basic. Lithium does not combine with hydro- 
gen ; it displaces the hydrogen of acids to form salts, com- 
bines readily with negative elements, and is electro-posi- 
tive to nearly all other elements. Beryllium, 9, is the sec- 
ond member of the series. Unlike lithium, it is not oxid- 
ized in the air at ordinary temperatures. It forms an oxide 
of the type RO, which is moderately basic, two atoms of 
the radical uniting with two of oxygen, or one with one. 
It does not combine with hydrogen ; it displaces hydrogen 
from many acids, and combines with most negative ele- 
ments, but is not so positive an element as lithium. Bo- 
ron, 11, forms the oxide B 2 3 , two atoms of it uniting with 
three of oxygen. This oxide is more acidic than basic, 
combining with water to form a weak acid, while it pro- 
duces salts only by interacting with the strongest of the 
acids. Like the metals, boron combines directly with sul- 



& I « 



s * 3 § ■ 



5 1 
§ 1 



Sv» 






St 9 

III 



g 

- 












II 



i 



— — 



p i 
























j a 



- pj 



- 



8 






■J R 



~ - - 



a i 



H 



— ' a 



s * 

5 






= i i 



I i 

- c 















j 









I - 1 



.? P ■ 



- 









g a 
i. 



M H 









c a 









a 



- 






98 CHEMICAL PRINCIPLES. 

phur, nitrogen, and the halogens, but, unlike them, it is 
a non-conductor of electricity, and is thought to combine 
with hydrogen. Carbon, 12, comes next. It forms an 
oxide of the type K0 2 (carbon dioxide), which is acidic, 
though the acid formed from it is weak. Carbon does not 
replace the hydrogen of acids to form salts, and it forms 
a compound with hydrogen of the type EH 4 . Nitrogen, 
14, forms the oxide N 2 5 , which is strongly acidic. It 
does not displace the hydrogen of acids, and it forms a 
hydride, NH 3 , which contains one less atom of hydrogen, 
than the hydride of carbon, and is alkaline. Oxygen, 16, 
combines with two atoms of hydrogen to form a neutral 
substance, H 2 0. It combines with all the positive elements, 
and all the negative elements except fluorine. It is electro- 
negative to most of the elements. Fluorine, 19, is the last 
element in this series. It is the farthest from lithium in 
position, and the most different from it in properties. Its 
hydrogen compound contains one less atom of hydrogen 
than that of oxygen, and is an acid. Fluorine is decidedly 
electro-negative ; it does not displace the hydrogen of acids, 
but forms compounds with metals and not with non-met- 
als. While lithium becomes oxidized in the air at common 
temperatures, fluorine is not known to combine with oxy- 
gen at all. The element with the next higher atomic weight, 
sodium, 23, is a metal, and resembles lithium very closely. 
The next, magnesium, 24, resembles beryllium, which fol- 
lowed lithium ; and, going on in this way, we shall find 
that each of the seven elements, beginning with sodium, 
corresponds in character with one of the first seven. 
This periodic rotation of characters extends through the 
whole list of elements, and allows them to be arranged in 
a table, as on page 97, in which they follow each other 
in lines in the order of their atomic weights, while, at 
the same time, elements of like properties stand under 
each other in the columns. The members of the left- 
hand group have a decidedly metallic character ; but, 



oram fkaturh oi rare pablb 99 

•How the linefl across the table, we find thai the 
bailie or positive propertiee grow weaker, while non- 
metalli gative properties appear and grow stronj 

bo a gradual change of properties in going from 
the top to the bottom of the table. For instance, the 

number of metals in each lino increases. In the second 

■nly the first two elements on the 1. metals; 

in the third series the lint three are metals; the fourth 

ntainfl six metallic elements; and bo oil 

187. Other Features of the Table. — In series i and :>, 

.'ii the atomic weigh! of any element and 

the from 1 to 3*5, the average being about 

nee between the weight Of an element in 

tin second line and the one under it varies from 15 to I ;, 

the average being 18. It will be noticed that there is an 

column in the table, containing three triplets of 

elements. They do not belong to any of the ordinary 

. »ut the tirst three iron, nickel, and cobalt — form 

a sort of connecting chain between the end of senee I 

ginning In like manner the next 

three find a p] 8 and serie< i, and the 

• three stand between series LOand 11. In the fl 
. es of the table, hydrogen stands alone. It is so placed 
because it resembles Group I more than any other in 

pro ri of series i may he regarded as 

cant. Empty places will he noticed in several parts of 
la Thus, the element with the next higher atomic 
after molybdenum, ruthenium, LOS, bul its 

not belong in the ii 
niitii, so thai place is left vacant, and 

nn \- j i Group VIII. where i( 

left, for similar I it 

\sill he dl till 

. if not all, of them. 

will !>e ronp 

stand in found 



100 CHEMICAL PRINCIPLES. 

that the alternate elements are more like each other than 
they are like those that stand next to them. This rule, 
however, does not hold good throughout the table. Thus, 
while the even-numbered members of Group I — lithium, 
potassium, rubidium, and caesium — are very much alike, of 
the odd-numbered members, hydrogen must be regarded 
as standing by itself, and sodium strongly resembles the 
even-numbered sub - group ; copper and silver resemble 
each other fairly well, while gold is not much like them. 

188. Periodic Changes of Physical Properties. — The 
physical as well as the chemical properties of the elements 
vary with the atomic weights. Thus, in passing from left 
to right along any series, we shall find, with some excep- 
tions, that the specific gravity falls as the atomic weight 
rises. Take, for instance, the seventh line, and we have : 



Silver. 


Cad- 
mium. 


In- 
dium. 


Tin. 


Anti- 
mony. 


Tellu- 
rium. 


Io- 
dine. 


Atomic weights. 108 


112 


113 


118 


120 


12G 


127 


Specific gravities. 10*5 


8-6 


7-4 


7*2 


6-7 


6-2 


4-9 



Ductility, melting-points, volatility, conducting power for 
heat and electricity, crystalline form, and influence upon 
the refraction of light, likewise stand in relation to atomic 
weight. 

189. Uses of the Law. — This classification enables us to 
predict what will be the properties of the undiscovered 
elements which are expected to take the vacant places in 
the table, for we know that they must be intermediate in 
character between those next above and below, and to the 
left and right of them. In fact, there are elements now 
in the table which were not known when this classifica- 
tion was made. Gallium, 70, is one of these. Mendelejefl 
predicted that an element would be discovered, with an 
atomic weight a little above that of zinc, and foretold 
what its properties would be. When gallium was discov- 
ered, it was found to agree very closely with his predictions. 



THE QHHMICAL N0XKN0LAT1 B in] 

The properties of Boandium and germanium were likewise 
told by him. 

Be> ibling us to predict the finding of newelfr- 

■ r\ ioe in testing the accuracy of 

3. Tims, indium, uranium, molybdenum, 

and tellurium were not brought into exactly the nine 

as in the table as their propertiefl would place them, 

and Ifendelejefl bo I that recalculation would give 

mi somewhat different atomic weights from thoee then 

accepted. These predictions were, for the most part, con- 
firm 



OHAPTEB \. 

Tin: i iii:mi< \i. nomi:n< LATUR& 

190. The Science reflected in its Language. — The terms 
used in chemistry bear the impress of the various theoreti- 
. stages of tl 3 ne of them, as gold, diver, 

iron, were applied to substances thousands of yeai 

before I had taken a separate form. The al- 

che- the first chemists, and they worked under 

d influence <>f astrology. Names still survive 

tha4 •■ fancied relations of sul to celestial 

tsilver was associated with Mercury; silver 

H,n ( hence lunar caustic) ; and the name 

npound of iron, ig a vestige <>f the 

Old ass 1 with Mar.. The alehem 

had a CTUdi D of -pirits in Nature, and 

ktQe pr« ►«] u<-t - accordingly, as spirit of 
wii. ( hartsh< 

bemical the 

i \s ith the French about 

Inn .ire ago, has bwn of immen • .-••niee, h.uh in 

iffusion <»f th. science. \N I 



102 CHEMICAL PRINCIPLES. 

the facts of chemistry were few, and its theory simple, the 
terminology, which conformed to the dual doctrine, was 
also simple and satisfactory. But as facts of all orders 
rapidly multiplied, and assumed new relations, the old sys- 
tem of expression was disturbed ; and, with the changes of 
theory, the nomenclature was unsettled at various points. 
There is still some want of uniformity among authorities 
in the use of chemical terms ; but general agreement 
upon a systematic chemical nomenclature is being rapidly 
attained. 

191. Naming the Elements. — The names of the ele- 
ments generally given have been expressive of some lead- 
ing quality, real or imaginary. Thus, oxygen received a 
name signifying acid-former ', while chlorine takes its name 
from its greenish color ; iodine, from its violet vapor, and 
phosphorus from its being luminous in the dark. Simi- 
larity of properties is sometimes indicated by similarity of 
termination, as chloric, bromine, iodine ; while the metals 
discovered in modern times are marked by the termination 
urn, as platinum, thalliwra, etc. 

192. Naming of Compound Radicals. — These sub- 
stances, which, as we have seen (160), are analogous to 
elements, are generally named from one or more of their 
constituents, or from some compound into which they 
enter. The terminal syllable, generally, is yl. Thus, the 
supposed radical consisting of one atom of hydrogen and 
one of oxygen is called liydroxyl, and that composed of 
one atom of oxygen and one of carbon, carbonyl. Excep- 
tions to the forms given are found in the case of cyanogen, 
and in the numerous compounds formed of carbon and 
hydrogen, or of carbon, oxygen, and hydrogen, whose 
names frequently bear reference to the number of their 
carbon-atoms, as, for example, hexyl, octyl, etc. 

193. Naming of Acids, Bases, and Salts. — The hydroxyl 
acids, which, as we have seen (163), have the general type 
ROH, take the name of the negative element which they 



NAMING OF U'lns, BASES, AND SALTS. J..;; 

tain. The ending u is given bo this name if the acid 
-.tains a large proportion rgen,and the ending 

if it contains a smaller proportion. Tims: 

UN N i'l. IIj> ( \ is Sulphurfc add. 

UN' ll.x »., i- Sulphumifl add. 

When more than two acids are formed with the same 
radical, the 3 . under, and par, oyer, arc em- 

ployed to distinguish them. Tims, /////'onitmns acid, 

11 \ tains lea 1 than nitron ihloric acid, 

HCIO* contains more oxygen than ohloric acid, EOlOa* 

in which sulphur takes the place of oxygen pre- 

to the name of the negative element. Tims, 

E(C1 id, H(ON)S i£ sulphocyanic acid. 

irhoee type is 1MI. also take the 
name of the negative radical which they contain, hut with 
the prefix hydro. They all have the ending fe, hut in 
this case it has cial meaning. Thus: EC1 is Hy- 

drochloric acid, II ( ( ' N ) is Hydrocyanic acid. 

Salts, ii will be ivr l, are formed from acids by 

lie hydr the acid by a positive radical. 

h the name of the acid and that of the substituted 

included in the name of a Bait, in order 

ish it from all others. The name of a hydroxy] 

to Hi when it is applied to 

a salt. Thi 

Sol] Sulpha 

u 1 U 

U 
u 

■ 

S • I ; 
80 also, sal* called sulpli 



104 CHEMICAL PRINCIPLES. 

CaS0 4 , calcium sulphate ; BaC0 3 , barium carbonate. Salts 
of hydrogen acids drop hydro from the name of the acid 
and change the ending to ide. Thus, sodium substituted 
in hydrochloric acid forms sodium chloride, NaCl ; potas- 
sium with hydrocyanic acid forms potassium cyamrfe, 
KOK 

Bases have the general formula, EOH, and they are 
named as if they were salts of water, regarding water as 
an acid. Thus, NaOH is called sodium hydrate; Ca0 2 H 2 
is called calcium hydrate, etc. 

Oxides, which are compounds of other elements with 
oxygen, take the name of the other element followed by 
oxide. If the quantity of oxygen in the molecule is large 
proportionately, the name of the other element takes the 
ending ic; if there is but little oxygen, it takes the ending 
ous. The same endings are used for other compounds in 
which the elements unite in more than one proportion. 
Thus : 

Feme oxide is Fe 2 3 . Stanmc chloride is SnCl 4 . 

Ferrous " FeO. Stannous " SnCl 2 . 

Where even more than two compounds of the same ele- 
ments are formed, a system of prefixes is used to distin- 
guish them. The compounds of nitrogen and oxygen 
consisting of two atoms of nitrogen united with one, two, 
three, four, and five atoms of oxygen, are often called 
nitrogen monoxide, dioxide, trioxide, tetroxide, and pent- 
oxide. An exception to the previous rules is made with 
compounds consisting of carbon and hydrogen ; these are 
so very numerous that the above methods can not be 
rigidly applied to them. 

194. Chemical Formula. — The notation and use of sym- 
bols have been already explained (144). Chemical com- 
position is expressed by joining these symbols ; and thus 
written they constitute chemical formulas. An empirical 
formula is one which states only what substances and 



CHEMICAL P0RMU1 LOS 

i thrin or number of atoms form a 

compound j Formula aims to express the mannef 

of atomic grou] the way the elements arc combined* 

Tne empirical formula for alcohol is c.H,<>, the rational 

formal I .OH, a compound of ethyl and hydroxyL 

w hen the atoms of a group arc more closely connected 

themselves than with the other constituents of the 

tnpoundfOr when they play the part of a compound radi- 

parated from the rest by a comma or period, 

inclosed in a parenthesis, or are represented by a single 

i. as in the i yanogeu i< I N ). Thus the 

tation may be written — 

Eg, ( -.\.= Bg + 20M or 
HgOy, = Hg + 2 i 

The pli atomic groups. 

What are called gr >r structural formulas are fre- 

quently used to show the structure of molecules, or how 
tli» I the graphic for- 

mula of mercuric cyanid 

\ < _ Bg-0«N 

195. Chemical Equations. The results of chemical re- 
:.].rvscntr<l in the form of equations, which de- 
ad npon the principle thai nothing is lost in the 

OIL The bodies to ; I upon i 

placed at the left, ;_ r n of addition 

+ . '1 • ii;it the products of 

ht equal th< 
at * quation also implies that the molecul 

those written upon the 
H t CaO,H 

ale 
water, the pr mi 

. 



PART III. 
DESCRIPTIVE CHEMISTRY. 



196. Classes of the Elements. — The elements are often 
divided for convenience into the two classes of metals and 
non-metals, or metalloids. This division is not an exact 
one, however, for some elements have partly the character 
of metals, partly that of non-metals, so that they seem 
somewhat out of place in either class. In the table of the 
Periodic System, most of the elements near the upper right- 
hand corner are non-metallic, but in passing to the left and 
downward metallic properties appear and grow stronger, 
till in the lower left-hand corner are found only elements 
that are unquestionably metals. 

197. Non-Metals. — The elements commonly put to- 
gether in this class are mostly non-conductors of heat and 
electricity ; when solid they are nearly all brittle, and they 
form acidic oxides. When liberated from combination 
with metals by electricity they appear at the positive pole 
of the battery; hence, because opposite electricities attract 
each other, the non-metals have been named negative ele- 
ments. 






HTDROGKN jo7 

OHAPTEB XII. 

H \ DROO 

t, 1; l v >uanti\;iK ikv, I; Sju riiic (Jravity, 1. 

198. Its Position. — In entering upon the description 
the properti bemioal substances we begin with 

hy hich i> taken m the anil for the atomic weight 

the elements. It Lb of great importanoe in nature, 
I bb in chemical theory, and is bo peculiar in itscharao- 
oonveniently classified with other 
I bo will be considered by itself. 

199. History. — It was known by Paracelsus, in the 
th century, that when iron La dissolved in sulphuric 

1 a kind of air is given off. It was shown by Boyle, in 

that this air would hum, and by Lemery, in 1700, 

that it would exploda But the first exact experiments 

upon it were m udish in L766,and it was called 

by him ' v. In 1781 he made the great dis- 

- the sole product of the combustion of 

therefore gave it the name hydro- 

. from two Greek word- meaning water-former. 

200. Occurrence in Nature. — Hydrogen is universally 
diffused, and in combination takes in active and varied 

rations of natur 

of all livinj changes contribute to 

carry on the processes of life. It is pr e s en t in nearly all 

classes [1 formi one ninth of theweight 

- a part of the substance of toj rch, 

i other imports) Formerly \\ Id 

• hvdroj i nature ; but il 

- gases, in meteoric 

masses in tl are. 

201. Preparation. Wat r, which impound 



108 



DESCRIPTIVE CHEMISTRY. 



hydrogen and oxygen, is the substance from which hydro- 
gen is usually obtained. There are several ways of pre- 
paring the gas, the 
simplest of which 
consists in separating 
it from the oxygen by 
means of sodium. A 
test-tube full of water 
is inverted and held 
with its mouth dip- 
ping into water in a 
large dish (Fig. 59). 
A bit of sodium the 
size of a pea is 
brought under the 
open end in a spoon, 
when it immediately 
begins to dissolve, 
and bubbles rapidly rise from it into the test-tube, dis- 
placing the water. The sodium has decomposed the 
water, setting free a part of the hydrogen, which has been 
collected in the tube, and combining with the oxygen and 
the rest of the hydrogen to form sodium hydrate, which 
dissolves in the water. The following is the reaction 
which takes place : 




Fig. 59.— Liberation of Hydrogen by Sodium. 



Na, + 2 H 2 

Sodium. Water. 



H 2 + 2 NaOH 

Hydrogen. Sodium Hydrate. 



The sodium, when taken from the naphtha in which it is 
kept, should be wiped on filter-paper and used at once. 
A piece of wire gauze bent round the bowl of the spoon 
will keep the sodium from floating out of it. 

The power of extracting hydrogen from water is com- 
mon to many metals, but some of them act only when 
heated. Red-hot iron, in contact with steam, combines 
with the oxygen, and hydrogen is liberated. When passed 



PREPARATION OF HYDROi 



109 



through a red-hot tube of platinum, steam is also decom- 
posed into its elements, the metal, however, undergoes no 
. A current of electricity also breaks up water into 
. which may be oolleoted separately (8 
202. By the Use of Zinc. — The method most commonly 
used for pn d is based on the action of di- 

lute sulphuric acid upon small pie inc. The rinc 

ad in ■ two-necked bottle (Fig. 60) and covered 




Fio. CO.— I 

with water. The tube, with ■ funnel at the top, admits 

I, when the actional once begins; thegasbubb 
u]» freely and passes oil through the benl tube, which 
delivers it und< itfa of an inverted jar which 

rests upon a support below the surface of the water. A 
vessel for the collection <>f gases, in tl . i- '-all. 

ISUally a tank, mad< 

tin, in which j Slled with water; inverted, and t ; 

ihelf, the water in ti • ting su] 

■ 

_ r a- they ni;; outh doi 

■■••- «»f window-glass, and k«-j»t f<»r u>e. In 
reaction the sulphuric acid 

Jphate 



110 DESCRIPTIVE CHEMISTRY. 

formed. The water only serves to dissolve the zinc salt, 
which, in the absence of water, would soon cover the metal 
and prevent the action of the acid. The changes are rep- 
resented by the following equation : 

H 2 S0 4 + Zn = ZnS0 4 + H 2 

Sulphuric Acid. Zinc. Zinc Sulphate. Hydrogen Gas. 

Hydrochloric acid serves as well as sulphuric acid. The 
process then is : 

2 HOI + Zn = ZnCl 2 + H 2 

Hydrochloric Acid. Zinc. Zinc Chloride. Hydrogen Gas. 

203. Physical Properties. — When prepared in this 
way, hydrogen has a disagreeable odor, arising from the 
impurities of the materials employed ; but pure hydrogen 
is a transparent, tasteless, inodorous gas, very slightly 
soluble in water. It does not support respiration, and 
animals immersed in it soon die. When mixed with air 
it may be breathed without immediate injury, but from 
its thinness or tenuity it imparts I squeaking tone to the 
voice. By a pressure of 650 atmospheres at —140° C it 
is converted into a steel-blue liquid, which, when evapora- 
tion is permitted, partly congeals to grains of metallic 
appearance. 

204. Its Lightness. — Hydrogen is the lightest of all 
known substances, being 14| times lighter than air, 16 
times lighter than oxygen, and 11,000 times lighter than 
water. Hence it may be transferred from one jar to 
another by pouring upward. Soap-bubbles filled with it 
rise to the ceiling, and it gives the greatest ascending 
power to balloons ; though they are usually inflated with 
a hydrocarbon gas, the lightness of which is due to the 
hydrogen it contains. Sound travels in it three times as 
fast as in air. Owing to the fineness of its molecules it 
will often escape through the joints of apparatus that are 
perfectly tight to other gases ; and a stream of it directed 



PROPERTIES OF BYDRtt 1 [ \ 

agii: _rnhl-leaf passes thmiiLrh >«» 

rapidly that it may ;he 
: ilitTusihle <>f tin 

205. Chemical Properties. 1 1 \ • 1 1 ot Bup- 

m, hut hums in air. It has great affinity 
for the Don-metallic elen aid bat little for the 

With it appears to form all' 

II. 3 chemical Baid to be metal 

place in the metallic part of the table on | 
te. Its compounds with one other element 
ailed hydrides. It is an essential constituent 
ids. In the jj s hydroj >m- 

bined with arming the molecule 1I-II. 

206. Inflammability and Explosiveness.— If a j. 
hydrogen in th ited it hums with an intensely 
hot flame, which is not at all luminous when th< 

pure, but uc tint bluish light, owing to the 

[phur or some other impurity. The only 

duct of the combtu If hyd and 

. gases ar I in the proportion to form wal 

that is, two rolumefl oi hj to one <>f o and 

mixture ifl then ignited with a match or an electric 

atly combine i ith a sharp report 
though less in- 

r with two 

of hyd 

^— 

a i 

perimenl 
riioul T> 




112 



DESCRIPTIVE CHEMISTRY. 




Fig. 62.— Experiment illustrating 
the Properties of Hydrogen. 



find out whether the gas coming from the apparatus is 
entirely freed from air, collect a test-tube full of it, and, 
keeping the tube mouth downward, light the gas. If 

it burns quietly, there is no 
danger ; a whistling sound, how- 
ever, shows an admixture of air. 
That hydrogen is lighter 
than air, that it will burn and 
explode, but does not itself 
support the combustion of or- 
dinary bodies, may all be shown 
by a very simple experiment 
illustrated in Fig. 62. If a jar 
of hydrogen is held mouth 
downward, and a lighted taper 
introduced, it is extinguished, 
while the gases take fire and 
burn at the mouth of the jar. 
If the jar is inverted, the escaping hydrogen unites with 
air, and there is a slight explosion. 

207. Condensation of Hydrogen. — But hydrogen and 
oxygen may be ignited without the application of fire. 
The metal platinum can be converted into a kind of 
powdery condition known as plantinum-sponge. If a 
jet of hydrogen is directed against a little ball of this 
sponge, it instantly becomes red-hot, and remains so as 
long as the current lasts. Dobereiner's lamp depends 
upon this principle. The theory of it is that oxygen is 
condensed within the fine pores of the metal, and the hy- 
drogen also being condensed by it, their molecules are 
brought within combining range, and union results. But 
the porous condition of the metal is not essential to this 
action. Clean strips of platinum will condense the gases 
upon their surface sufficiently to cause rapid combination. 
The relations of platinum to water and its elements illus- 
trate in a striking way the influence of heat on chemical 



• MVi.rsioN OF HV|)KO« 1 13 

ehanger. 1 1 « »t platinum decomposes water into its de- 
ments; cold platinum, on the contrary, unites them, 

208. Occlusion of Hydrogen. —Bed-hoi platinum, pal- 
ladium, and iron, allow hydrogen to pass through them 
freely, and when oold are capable of retaining considerable 

tlu k gas. These metals also absorb and retain 
hydrogen when it is presented to them in a oascenl Mate 
tham, who named tfa has Bhown thai 

palladium takes ap more than 900 times its volume of 
ii\ rod that the product is a white metallic solid. 

11' ompound as an alloy, consisting of pal- 

ladium idified hydrogen, which he helieved to he a 

al, and called hydrogenium* Hydrogen in oombina- 
1 by metals, and undoubtedly has strong 
es with them ; bu1 it U also replaced by chlorine, and 
th the non-metallic elements are aa aumer- 

;. and as important, as those with 

the ' 

209. Chemical Via.— The chief use of hydrogen in 
mieal operations is as a reducing agent j thai is, asa 

of withdrawing oxygen and chlorine, for which it 

affinity, from their compounds with other 
< with these two suhstances, 
for- iter or hydrochloric scid. Ii is most active in 

this way when in the fUUCtnt $kU< i L38). 



114 DESCRIPTIVE CHEMISTRY. 



DIVISION I.-NOMETALS. 



CHAPTER XIII. 

THE HALOGENS. 

210. The elements fluorine, chlorine, bromine, and 
iodine form a well-marked chemical group, exhibiting a 
regular progression of properties. At ordinary tempera- 
tures, fluorine and chlorine are gases, bromine is a liquid, 
and iodine a solid. Chemically they are highly active 
substances, and are not found uncombined in nature. 
They unite with metals to form a class of compounds of 
which common salt is the type. Hence they have been 
called halogens, from two Greek words meaning salt- 
formers. Their salts also exhibit a sequence of properties 
in many cases : thus, fluoride of silver is very soluble in 
water ; chloride of silver is insoluble in water but soluble 
in ammonia ; the bromide is only slightly soluble in am- 
monia, while the iodide is insoluble in it. 

§ 1. Fluorine. 

Symbol F. Atomic weight, 19; Quanti valence, I; Specific Gravity, 1*3. 

211. History and Properties. — This element was un- 
known in the free state until recently obtained by decom- 
posing hydrofluoric acid with an electric current. Its 
most frequent natural compounds are the two minerals 
fluor-spar (calcium fluoride) and cryolite (aluminum and 
sodium fluoride). In consequence of its great affinity for 
other substances, combining with the material of any con- 
taining vessel, it has not yet been satisfactorily isolated. 
Fluorine is a gas at ordinary temperatures, and is said to 




B LLOGENR 1 i;> 

haw a yellow color. It combines with most <>f the ele- 
ments, but is the only one which will not combine with 

212. Hydrofluoric Acid, HP, abstanoe ifl pro- 

duoed wbei fluor-spar) is acted upon 

inlphurii ith 

the application 

Hydrofluoric 
arid 

(»f lead of platinum 

1,1 tt.-lUklDg Hydros 

kepi in gutta-p 

ttles. As thus obtained it is a colorless gas, which 
to a liquid l>\ a freezing mixture. < hi 
affinity for water, th< 
with the aqueo wr in the air, forming cloudy tun 

; if inhaled intensely irritates the moist lining <>f the 
lungs. I hing characteristic of hydrofluoric 

ion on . This may be shown 

bj wdered calcium fluoride, made inti 

with sulphuric acid, in a leaden 

y/^ cup (1 and covering it a ith a 

jL pn \ iously ami pred on 

g l idc with wax through which let- 

•i traced with a sharp- 

iM.int. ! -tirk. The routed ride i 

iwnward and the cup Qtiy 

n <>r f. { the 

glass :T the wax « if id of a little 

.ill be I into the 

glass. T - the 

aQicatea <»f which glass Lb oomp ( the 
irhich firmly adh 
posed lii 



116 



DESCRIPTIVE CHEMISTRY. 



to etch the marks on the glass tubes of thermometers and 
other instruments, and the names on glass bottles used in 
laboratories and drug-stores, where paper labels would be 
destroyed by corrosive substances. 

§ 2. Chlorine. 

Symbol, CI. Atomic Weight, 35*5 ; Quantivalence, I, III, V, and VII ; 
Specific Gravity, 2*47. 

213. History. — Chlorine was discovered by Scheele, in 
1774, but was long regarded as a compound. In 1810 
Davy established its elementary character, and gave it the 
name it bears, from the Greek chloros, yellowish green. 
It is never found free in nature, but exists abundantly in 
the mineral world, in combination chiefly with the metal 
sodium, as common salt. 

214. Preparation. — The usual method of obtaining 
chlorine is by the action of hydrochloric acid on manga- 
nese dioxide. The dioxide is placed in a flask provided 
with a tube for pouring in the acid, and one for the deliv- 




Fig. 65.— Preparation of Chlorine. 



ery of the gas. To the delivery-tube is attached an inter- 
mediate bottle containing sulphuric acid, a powerful ab- 



PROPERTIES OF CHLORINE 



117 



florlvn: r, which dries tin- gafl and also retains the 

hyd ic acid, which might be oarried off by the 

chlorin* m this bottle it passes through a tube 

to the recei yer 5). A little acid is first poured in 

I well shaken ap with the manganese, in order to wet 

ry portion of it ; more acid i> then added, and a gentle 
heat applied, when the gas is copiously given oft The re- 
■n may be thus expressed : 

IfnO, h2HCl= Mncl, + -jll v o-f. OU. 

If collected in a pneumatic trough, the water should he as 

> can l>e used, in order to lessen its absorption of the 

gas. It may also be 

! by display 
incut, in which case a 
delivery-tube bent at 
3 used, 

and this is made bo run 

n into ; 
nearly to the bottom. 

chlorine, being 

rier than air. ool- 

the bottom of 

. and * 

gre<-: lor of the 

gas will indicate when 
the Oiled 

Chlorine 

From corn- 
aid of 

sulphuric ioid ami 
din. 
r hut less 

'it method*. 

215 Properties. M 

Ohl of the Fio.ac «en. 




118 



DESCRIPTIVE CHEMISTRY. 



most energetic of bodies, surpassing even oxygen under 
some circumstances. At ordinary temperatures it is a yel- 
lowish-green gas (Cl-Cl) ; but by a pressure equal to six 
atmospheres, at 0°O, or by exposure to a cold of —34° C, 
it may be condensed to a transparent, yellow liquid of 1*38 
specific gravity, which has never been solidified. The gas 
has a peculiar suffocating odor, and if inhaled, even when 
considerably diluted, produces distressing irritation of the 
throat and lungs. When respired, however, in very minute 
quantities, it is not only harmless, but is said to be bene- 
ficial to those affected with pulmonary disease. Chlorine 
burns in hydrogen (Fig. 66) though not in air, and hydro- 
gen also burns in chlorine (Fig. 07). Many bodies burn 




Fig. 67. — Hydrogen burning in Chlorine. 



in it readily and some take fire in it spontaneously, such 
as phosphorus, finely powdered antimony (Fig. 68), zinc, 
and arsenic when brought into dry chlorine gas. Many 



- OF <!Hoi:l\K 



119 




nic compounds, rich in hyd] led by 

rapidly as often to burst into flame. A ; paper 

saturated wit ! turpentine, and plunged into a jar 

filled with ohlorin< 

• 
and usually ignites, from the 
sition ol the 
tnrpenti] 

bout 

■nd s half times its own 

bulk of chlorine, the solution 

. and 
smell of the gas. If this so- 
lution Lb oooled down to 

riline hydrate 
Jorine is formed, haying 
formula CL lOHt< >. I. 
ui«l chlorine may be readily 

from tl. by hermetically sealing them 

in a curved tube, and applying s gentle heat This lib- 

tin* chlorine, which, prcssin;: upon 
tie condition of s liquid. It 
distinguished from the water pn 
by its yellon Chlorine solution readi- 

tnposes chlo- 
• 
free oxygen ; I •Mary to 

216. Uses. 

res the I or- 

dinary fabrics, ind 



Flo. 88. - Combust 




120 DESCRIPTIVE CHEMISTRY. 

bleach printer's ink. Woolen and silk goods are injured 
by it, hence it is principally used in bleaching cotton cloth 
and rags of which paper is to be made. Without water 
chlorine can not bleach ; hence it must be used in the form 
of solution (chlorine water), or at least the gas must be 
moist. It acts by decomposing the associated water, unit- 
ing with its hydrogen, and setting oxygen free, which, in its 
nascent state, oxidizes and decomposes the coloring parti- 
cles. One of the products of its action is hydrochloric acid, 
which will injure the bleached articles if it is not promptly 
neutralized. For this purpose a solution of calcium sul- 
phite is used. Its strong affinity for hydrogen, which en- 
ables it to tear apart the constituents of water and set free 
oxygen in its nascent or most active state, makes chlorine 
an important oxidizing agent. It is often used in the la- 
boratory for this purpose. The energetic chemical action 
of chlorine renders it very useful as a disinfectant. Sil- 
ver nitrate (lunar caustic) added to a solution containing 
chlorine, or a soluble chloride, gives a white precipitate of 
silver chloride, AgCl, which on exposure to light changes 
first to violet, and then to black. Silver nitrate is the 
test for chlorine. This element is largely used in the prep- 
aration of chloride of lime (bleaching-powder), in which 
form it is made available as a bleaching or disinfecting 
agent. On account of its oxidizing property, nothing that 
can rust should be left where it is used. For disinfecting 
the sick-room, a quarter of a pound of chloride of lime is 
dissolved in a gallon of water, and a piece of flannel wet 
with this solution is hung up in the room. The carbonic 
acid in the air causes a small but constant evolution of 
chlorine or an oxide of chlorine. For active disinfection, 
some bleaching-powder and sulphuric acid or strong vinegar 
should be mixed on a plate and the plate set on a hot brick. 
The room must then be closed and left for some hours. 

217. Hydrochloric Acid, HC1 (Muriatic Acid). — This 
is the only compound of chlorine and hydrogen known. 



HYDROCHLORIC ACID 



121 




Priestley first obtained it 
ft gas in l 778, and I >a\ y 
tabliahed it > composition 

in 1M<>. It OOOOT8 in na- 
ture ftmong the gaseous 
products of volcanic erup- 
tions. A mixture of chlo- 
rine and hydrogen ibises 
when exposed to direct 
sunlight, Lb converted, 
with violent explosion, 

% into hydrochloric acid. 
Each of the also 

m and hums freely in an atmos- 
phere of the other yield- 

the same product. If a jar is filled one half with 

hydn her half with chlorine, and the g 







122 DESCRIPTIVE CHEMISTRY. 

ignited at the mouth, an explosion takes place ; and white 
fumes of hydrochloric acid are formed. A towel should 
be wrapped around the jar to prevent the pieces from 
scattering in case it bursts (Fig. 70). Hydrochloric acid 
is generally prepared by the action of sulphuric acid on 
sodium chloride (common salt). The reaction is ex- 
pressed by the equation : 

2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1. 

As the gas is greedily absorbed by water, it must be col- 
lected over mercury, or by displacement. Fig. 71 shows 
a convenient arrangement for its preparation. 

218. Properties and Uses. — Hydrochloric acid is a 
colorless, pungent gas, irrespirable, very irritating to the 
eyes, and extinguishes flame. It is somewhat heavier 
than air, having a specific gravity of 1*24. Under a 
pressure of 40 atmospheres at —10° C, or of two atmos- 
pheres at —70° C, it condenses into a colorless liquid of 
1-27 specific gravity, which freezes at —116° C. Hydro- 
chloric acid is exceedingly soluble in water, which, at 
0° 0., absorbs 500 times its volume of the gas. This 
solution is much used in the laboratory as a chemical re- 
agent. 

219. Compounds of Chlorine and Oxygen. — The com- 
pounds of chlorine and oxygen are unstable, and most of 
them explosive. Besides, there are four compounds with 
hydrogen and oxygen known as oxyacids of chlorine : 

Chlorine monoxide, C1 2 0* Hypochlorous acid, HCIO. 
Chlorine trioxide, C1 2 3 . Chlorous acid, HC10 8 . 
Chlorine tetroxide, C1 2 4 . Chloric acid, HC10 3 . 
Perchloric acid, HC10 4 . 

220. Chlorine Monoxide, C1 2 0. — This compound may 
be obtained by passing dry chlorine through a tube filled 
with mercuric oxide. A portion of the chlorine takes the 



BROMINE IJ3 

place of the oxygen, forming mercuric chloride, whik 

another portion unites with the oxygen, at the moment of 

on, forming chlorine monoxide. It is a red 
liquid, boili . ' C, and giving a reddish-yellow | 

haying explosive and bleaching properties. 

221. Chlorine Tetroxide, ( h >«. — When potassium ohlo- 
, KCIO,, is made into a paste with sulphuric acid and 

cooled, and this pac autionsly heated in a glass re- 

water-hath, a deep-yellow gafl is evolved, whieli 
. Only he collected hy displacement. Chlorine tetroxide 

has a powerful odor, and, if heated, explodes with great 
ence. It may he liquefied by cold. Water absorbes it, 
tlie solution pose strong bleaching properties. 

222. Chloric Acid, IK do, — This compound may he 
bained by decomposing a solution of potassium chlorate 

with a solution of hydro-fluosilicic acid, the products 

ing an insoluble potassium fluosilicate, and a dilute so- 

lution of chloric acid, which, by cautious evaporation at a 

low temperature, may he concentrated to the consistence 
rup. It is a very unstable compound, l>cin# easily 
composed, especially by organic matter, which it BOme- 
tiines ignites. 

I, Bram 

Atomic v ■ • m a, L \ . ind vn • 

■ i *. 

223. Higtory and Preparation. This substance was 

•rained by Balard in 1826. It- Dame l- derived 

from ti i •.•!!< -h." Bromine is no! found 

After the 'ion of the crystalliiab 

m sea-v i other brin< H ;i solution of 

re soluble sa other-li< 

ittern i- rich in bromides, and. it with 

inganese dioxide and sulphuric acid, chlorine is 1 

from t 'I'll,' chlorine, in its turn, 

-places the hromiiM- from the bromides, and tie 



124 



DESCRIPTIVE CHEMISTRY. 



are collected in a cooled receiver, where they condense into 
a liquid. 

224. Properties and Uses. — Bromine, at ordinary tem- 
peratures, is a deep brownish-red, heavy liquid, and has a 
peculiar, irritating, disagreeable odor. At —22° C. it 
solidifies to a hard, brittle, scaly mass, having a dark lead- 
gray color and semi-metallic luster. At 63° C. it boils, 
forming red vapors. It dissolves sparingly in water, more 
readily in alcohol, and in all proportions in ether. It is 
an active chemical agent, having properties resembling 
those of chlorine, and is a violent poison. 

225. Hydrobromic Acid and the Bromides. — Like chlo- 
rine, bromine forms an acid with hydrogen, HBr, which 




Fig. 72.— Making Hydrobromic Acid. 



resembles hydrochloric acid in character. It may be made 
from bromine and water by the aid of phosphorus (Fig. 
72). 

Salts of hydrobromic acid, called bromides, are formed. 
They are all solid, nearly all soluble in water, and resemble 
the chlorides in other respects. Their chief uses are in 
photography (silver bromide, AgBr) and in medicine 






IOPIXK. jo;, 

ttassiuin bromide, ElBtj iron bromide, 1 uul 

ammonium bromide^ N 11 J»r). 

S Li 

Atomic- Weight, lS7j Quanttrakooe, l, III, V, ind vn ; 
iftc Qiai it}, M i. 

226. History, [odine was discovered in L812, in prod- 
la of decomposition obtained from the mother-liquor, 

which remains when the ashes of sea-weed, known as 

u kelp, w are leached, and allowed to crystallise. Hie name 

rived from the Greek word meaning violet, and 

olorof its vapor. It is not found native. 

Th' ration is similar to that of bromine. The 

ther-liquors are distilled with manganese dioxide and 

sulphuric acid, and the vapors condensed. 

227. Properties and Uses. — [odine is a grayish-black 
solid of metallic luster, and crystallizes in forms of the 
trimetr m. It melts at LIS C, and boils at 200° 

in a dense, beautiful, deep-violet vapor, which 
times heavier than air. [odine volatilizes even at 
ordinary temperatures, diffusing an odor somewhai similar 
to that of chlorine, though easily distinguished from it. 
It is sparing ble in water, more easily in alcohol and 

ether, or in aqueous solutions of itfl own salts, [odine 
colors starch-paste a beautiful deep-blue, this reaction 
g the mod delicate test of its pn It 

star ikin yellow, but is not so corrosively poisonc 

as chlorine or bromine. It is s p luctor of • ■'■ 

tricity. A dark-brown solution of iodine in alcohol (con- 
otaasium iodidt miliarly known as 

tore of ; i liniment 

228. Compounds of Iodine. //,/// I . Ill, 
closely resembles h readily decom- 

pO> from othrr 

Tl • 



126 DESCRIPTIVE CHEMISTRY. 

salts of hydriodic acid, resemble the bromides in proper- 
ties, and consequently in uses. They occur in sea- water, 
and are taken up in the growth of certain sea-weeds. 
These weeds are collected and burned, and the iodides 
are obtained from their ashes. Iodine also forms oxides 
and oxyacids. 



CHAPTEE XIV. 

TRIVALENT NON-METALS. — NITROGEN, PHOSPHORUS, 
ARSENIC, ANTIMONY, BORON. 

229. Like the halogens, the members of this group 
having the highest atomic weights melt and vaporize at 
the highest temperatures. In their combinations with 
hydrogen they are trivalent, and in some other compounds 
quinquivalent. Boron, although not exactly belonging to 
this group, may be considered as a connecting link be- 
tween it and the next one. 

§ 1. Nitrogen. 

Symbol, N. Atomic Weight, 14 ; Quantivalence, I, III, and V ; 
Specific Gravity, 0*972. 

230. Nitrogen Gas. — This gas was discovered by 
Rutherford, in 1772. Chaptal afterward gave it the name 
nitrogen, signifying generator of niter. It is very exten- 
sively diffused in nature, forming about four fifths of the 
atmosphere, in which it plays the important part of dilut- 
ing the oxygen, and adapting it to the conditions of life. 
It is a constant ingredient of animal tissue, and is never 
entirely absent from plants, while of many important 
vegetable products it is an essential constituent, as, for 
example, of the vegetable alkaloids. 

231. Preparation. — Nitrogen is most commonly pre- 



NITROGEN. 



127 







^.**»1 



I'lvjuiniiinn of Nitrogen. 



i by withdrawing the oxygon from n j>ortion of nir. 
A small bit of phosphorus ifl placed in a little cup and 

tted on the water in i 
pneumatic trough. It u then 

set on tire an* 1 a jar placed 

in Fig. 73. Tin* 

sphorus takes tlio oxygon, 

forming phosphorus pentox- 
yl hicli tills the jar with a 

white vapor ; hut tin 

absorhed bj the water, and 

nitrogen alone ifl left, the 

; to occupy the 

:* the vanished oxygen. 

There are a number of other ways of preparing nitrogen. 
When air is conducted over red-hot OOpper-turnillgB, its 

mbinefl with tin' copper and the nitrogen re- 
main-. Ammonium nitrite is hroken up by heat into 
nitrogen and water : 

MI 4 \<>,= X. + ^II.O. 

232. Properties. — Nitrogen 18 a transparent gas, witli- 

r color, which, at a temperature of —146 
i pressure atmospheres, may be condensed 

n liquid. It Lb remarkable for chemical inert- 
ness. It is irrespirahle ; animals placed in it quickly die, 

• from i- -ion, l»iit from lack of oxygen. 

A - introduced into it i> immediately 

I xm, titanium, silicon, and magnesium hum 

in it, with the formation of nitrides. I' ifl slightly soluble 

in wat. hundred volumes of the latter, at 1 .'» 

Kid a half of the gas. Ah 

/ with only a few 1 !••- 

■ ntaim-d in a large numh. r and 
Tariety of compound 

233. Ammonia ( II \ )(B 



128 DESCRIPTIVE CHEMISTRY. 

stance was known in ancient times, and was first described 
accurately by Black, in 1756. It is frequently met with 
in nature, being a constant product of the decomposition 
of organic substances which contain nitrogen. It is pro- 
duced by the decay of animal matter, and artificially by 
the destructive distillation of horns and hoofs, which are 
rich in nitrogen, but the chief source of commercial am- 
monia is the " ammoniacal liquor " of the gas-works. 
Ammonia gas is conveniently obtained by the action of 
one part of quicklime, CaO, upon two parts of ammonium 
chloride, NH 4 C1, in a glass flask or retort. The reaction 
is thus shown : 

2NH 4 C1 + CaO = CaCl 2 + H 2 + 2H 3 N. 

It will be seen that the calcium of the lime unites 
with the chlorine, forming calcium chloride, while water 
and ammonia are set free. The gas may be 
collected in jars, but it must be over mercu- 
ry, as water absorbs it eagerly. A more con- 
venient way to procure it is by the method 
A of upward displacement. The gas generated 
in the lower vessel (Fig. 74), being lighter 
than the air, accumulates in the upper por- 
tion of the inverted jar, displacing the air 
and expelling it downward. 
fig. 74.-Produc- 234. Properties. — Ammonia is a color- 
ing Ammonia. lesg gag of a pimgent9 caus tic taste, lighter 

than air (sp. gr. 0*59), and possesses strong alkaline prop- 
erties, changing vegetable red to blue and yellow to brown, 
whence it is called volatile alkali. It does not support 
combustion or respiration, only oxygen burning in it : 

2NH 3 + 30 = 3H 2 + N 2 . 

Ammonia, on the other hand, also burns in oxygen, giving 
the same products. It may be condensed by cold and 
pressure, both to the liquid and the solid state. Ammonia 



AMMONIA. 



129 



&> 




Fii,. . 



is rec . I by its odor. Also, if a rod dipped in hydro- 
chloric acid Lb brought near a source of ammonia, a 
white cloud is produced by the formation of 
ammonium chloride (Nll ; < it (Fig, 75). By 
d alight traoee of ammonia may 

235. Ammonia Water (Aqua Ammonim). 
— The solution <>f ammonia gas in water is 
calK'd ammonia water, or simply ammonia, 

I is the form in which this substance h commonly 
use<l. Prom the tart thai it was formerly obtained from 

horns of harts, the solution was called spirits of luirfs- 
hnrn. Ammonia water is prepared by passing ammonia 

gas into water, which absorbs it rapidly to the extent of 
700 times its own volume. The gas is evolved by gently 
beatings mixture of daked lime and sal-ammoniac, and 
the water into which it is passed is contained in a series 
of bottles. In making solutions of the absorbable erases 
several difficulties and dangers have to be guarded against 

The action in the generating flask Lfl liable to various 

interruptions, while the water in the bottles rapidly ab- 
sorb gas. This creates a partial vacuum, and the 
. that the water in the bottles flows back 

into th< thus putting an end to the process; also, 

if the gas is generated 

faster than it is absorbed, 

thei the risk of an 

explosion, unless there is a 
free outlet to the appara- 
tus. These d 
obviated by the arras 
iieiit known aa w 
bottl 

Th.- flask in which the 

with a safi which both ai i 







130 DESCRIPTIVE CHEMISTRY. 

ducing a liquid and as a protection against the above-men- 
tioned accidents. When the liquid is poured in, a portion 
of it is retained in the bend of the tube, acting there as a 
valve to prevent air from entering the flask. Each bottle 
has astraight safety-tube passing through the cork in the 
middle neck and dipping into the water. Air enters the 
bottle by this tube if a vacuum is formed, and the water 
rises in it if the pressure of the gas becomes too great. 
The other tubes serve to connect the bottles with the flask 
and with each other. 

If left exposed to the air, most of the gas escapes from 
the solution at ordinary temperatures, and it may all be 
driven off by boiling. Ammonia water is sometimes re- 
garded as a compound of NH 3 with H 2 0, dissolved in an 
excess of water, and is called ammonium hydrate, its 
formula being written NH 4 OH. But the ease with which 
the gas escapes from the liquid shows that, if there is 
chemical union, it must be very slight. 

236. Uses. — Ammonia is used medicinally in various 
ways. It is administered internally as a stimulant, and 
applied externally as a counter-irritant, and is the active 
constituent of smelling-salts. Mixed with olive-oil, it 
forms volatile liniment. It is the best antidote to prussic 
acid, but is itself poisonous in large doses. Its own anti- 
dote is some weak acid, as vinegar or lemon- juice. It is of 
many uses to the chemist, and also valuable in the house- 
hold for cleansing purposes. 

237. Ammonium (NH 4 ). — One reason for regarding 
ammonium hydrate as a definite compound is that it acts 
like a base in forming salts. Its graphic formula is 
(H 4 )^N-0-H. The single atom of hydrogen which is 
linked to the one oxygen-atom is replaceable by negative 
radicals, and the resulting compounds are termed am- 
moniacal salts. These salts are remarkable as being iso- 
morphous with certain potassium compounds, and when 
the formulas of any two of these isomorphous salts are 



AMMONUM t HI.OIUDK. 



i:;i 



•spared, it lb found that the atomic group II 4 N exactly 

[responds in function to the radical potassium. Thus 

in oomparing the formulas of the two well-known i><>- 

morplmus salts — 

r..ta>li-alum K .^< > 4 , Al,( S< >j .- 1 1 1 < > 

Ammonia-alum ( N 1 l 4 ).S< » 4 . A 1 {&( ) 4 ) .! \ \ | < ». 

we readily observe this analogy. On account of this re- 
markable fact, it lias hern assumed that the atomic group, 
11 4 \, must be very similar in character to potassium, and 
possessed of metallic properties. This radical has been 
named a um. It has not yel been isolated, hut an un- 

stable alloy of it with mercury, having the general character 
of the amalgams of ordinary metals, is produced by mixing 
m amalgam with a solution of ammonium chloride. 
238. Ammonium Chloride (NH4CI) (Sal-ammoniac). — 
This substance i- found native in many volcanic regions, 




the virinitv of burning OOal-mfaieS, and in gUaH0- 

►osits. WTien hydrochloric acid ami amu 
are brought together, they form dense white clouds of 
ammonium chloride, M may bo seen in ITig, 1 i 
remed t; 

Ml I IK 1 = MI 4 (T 



132 DESCRIPTIVE CHEMISTRY. 

When an aqueous solution of ammonia is neutralized 
by hydrochloric acid, crystals of ammonium chloride are 
produced, which have a sharp taste, and dissolve in three 
times their weight of cold water. Sal-ammoniac is chiefly 
obtained by neutralizing the ammoniacal liquor of the 
gas-works by hydrochloric acid. On evaporating the re- 
sulting solution, the salt appears in the form of the tough, 
fibrous crystals of commerce. It is volatilized by heat. 
Mixed with lime, which decomposes it and expels the 
ammonia, it is used in smelling-bottles. When heated 
with metallic oxides, it frequently converts them into 
chlorides, which are either fusible or volatile. This prop- 
erty makes it fit for cleansing the tarnish from metallic 
surfaces which are to be soldered together.. 

239. — Ammonium Nitrate (H 4 N) N0 3 is formed in 
small quantities during thunder-storms, and is sometimes 
contained in rain-water. Ammonium sulphate (H 4 N) 2 
SO, is a valuable fertilizer. Several ammonium carbonates 
are known, and the commercial ammonium carbonate, 
when purified, constitutes the volatile salts, or smelling- 
salts, of the shops, giving off ammonia gas. 

240. Oxides and Acids of Nitrogen. — Nitrogen com- 
bines with oxygen, forming : 

1. Nitrous oxide, or 

Nitrogen monoxide, N 2 0. Hyponitrous acid, HNO. 

2. Nitric oxide, or 
Nitrogen dioxide, NO. 

3. Nitrogen trioxide, N 2 3 . Nitrous acid, HN0 2 . 

4. Nitrogen peroxide, or 
Nitrogen tetroxide, N0 2 . 

5. Nitrogen pentoxide, N 2 5 . Nitric acid, HN0 3 . 

The oxides 1,3, and 5 are the anhydrides of the respective 
acids. The acids are formed by the addition of water 
with oxides : 

N 2 5 + H 2 = 2HN0 3 . 



HITROl S OXIDE, 



L83 



241. Nitrous Oxide (X,0) (^ 1/ //'/>). — 

impound was diaoovered, in L776, by Priestley, and 
further examined by Davy in L800, irho noticed the ex- 
hilarating effects produced l>v tlm respiration of tln> -a>, 
from which its popular name, u laughi ." is derived. 

It is prepared from ammonium nitrate by moderately 

heating this salt inailask. The aprs through a 

tube, and is Oolleoted in jars over watrr (Fi| Ii 




- 



ould )>♦■ allowed to stand for Borne time over water, to 
nitrous acid that may chance t<» be formed. 
The chemical change may !>.• represented by the equation, 

Ml ; \n,,=r-.'ll'» | N 

one molecule of ammonium nil Iding two m< 

: one «-f nitrogen monoxide. 
242. Properties ordinary temperature* nitre 

IDOI »lorlrs- , trai 

\Ae in ' "hi 

• three 6 

ipporter «>f comb ht- 

Ue plunged into the gag, and 



134 



DESCRIPTIVE CHEMISTRY. 



f ying the combustion of phosphorus almost equally with 
pure oxygen. A pressure of 50 atmospheres at 7° C. 
condenses it into a clear liquid which boils at about 
— 88° C, and may be frozen at about — 115° C. When 
breathed in small quantities this gas produces a transient 
intoxication, attended sometimes by an irresistible pro- 
pensity to laugh, and at others by a tendency to muscu- 
lar exertion, individuals being variously affected accord- 
ing to temperament. The gas should be pure, and even 
then the experiment is not a safe one for some consti- 
tutions. Inhaled in larger quantities it produces insensi- 
bility, hence it is now much employed by dentists as an 
anaesthetic. 

243. Nitric Acid (HN0 3 ). — This compound, formerly 
known as aqua-fortis (strong water), is not found free in 
nature, but has been known since very early times. To 




Fig. 79.— Liberation of Nitric Acid. 



prepare the acid, well-dried sodium nitrate, or potassium 
nitrate, is distilled with about 1*5 times its weight of con- 
centrated sulphuric acid. An excess of sulphuric acid 
is indispensable, because, if only the quantity required to 



NITRIC acid. 13J 

form the salt, Nl v « ».. were taken, the heat in for 

rfect disengagement of the acid would be BO high a 

induce decomposition of the product into oxygen, water, 
and nitrogen peroxide; bat if, as in the following equa- 

i, the sulphuric acid sulliees to form the Belt, Nall,>' 

the nitric arid remains intact The prooess Lb represented 
[nation : 

\a\<> + H-;S0 4 = XaIIS<> 4 + II\n 

Thai 18, one molecule Of BOdinm nitrate and one of sul- 
phuric acid furnish one molecule of nitric acid and one 

of acid BOdium sulphate. The receiver K in Pig 

kepi oool bya stream of odd water flowing oyer it, and 

by mean- of a netting. 

244. Properties— Nil ric acid is a oolorlees, mobile 

hquid, of varying specific gravity according to its strength, 

fuming in contact with the air, and possessed of an in- 

r taste and peculiar Bweetish-ns en! 

11. The pure acid, EINO , boils at 131 0. It is 

infl the skin, nails, and other 

imal sub yellow; it is therefore need to pro- 

dni ms upon woolen fabric* It is ilso 

iployed foretchii >pper, and for assaying or b 

In consequence <»f its large proportion of 
. it corrodes the metals with and 

he:. the most powerful <«f nvidizii ts. It 

powdered charcoal and <.il <>f turpentine, and 
iiorus BO rapidly M to produce an • 

don. Many of its compounds are distinguished by 
properties. !•- combination with 
nitro-gl 

, in minute 'pi. 
• • in question by a 1;: 

. in a t. 

and |M»ur carefully upon it a solution of green ritri 



136 DESCRIPTIVE CHEMISTRY. 

The presence of nitric acid will be evident if a brown 
ring appears at the zone separating the two liquids. 

245. Aqua Regia. — A mixture of hydrochloric acid 
with nitric acid constitutes the aqua regia, or royal wa- 
ter of the alchemists, so named from the power it pos- 
sesses of dissolving gold, the " king of metals," a property 
due to the presence of chlorine, which, at the moment of 
its formation, attacks metals with great energy. The pro- 
portions for the mixture are four measures of hydro- 
chloric acid to one of nitric acid. 

§ 2. Phosphorus. 

Symbol, P. Atomic Weight, 31 ; Quantivalence, I, III, and V; Specific 

Gravity, 1*82. 

246. Distribution. — Phosphorus is found in nature 
chiefly in combination with calcium. It is a never- failing 
constituent of the plants used as food by man and the do- 
mestic animals. It is an equally important ingredient of 
the bones of animals, which are chiefly built up of calcium 
and magnesium phosphates, while it also exists in different 
combinations in the blood, flesh, milk, and other tissues 
and secretions of animals. Phosphorus exists in several 
allotropic states, but is never found native. 

Phosphorus exhibits a remarkable exception to the law 
that the molecule of bodies in the gaseous state consists of 
two atoms. The atomic weight of oxygen is 16, and, com- 
paring equal volumes of oxygen and hydrogen, we find the 
former to be sixteen times heavier than the latter. But if 
we compare the weights of equal volumes of gaseous phos- 
phorus and hydrogen, we find the former to be sixty-two 
times heavier, although its atomic weight is 31. The 
molecule of gaseous phosphorus, therefore, consists of four 
atoms, which is also the case with arsenic. 

247. Ordinary Phosphorus (P 4 ). — This interesting sub- 
stance was discovered in 1669, by Brandt. Most of the 



PHOBPHORUE i;;; 

phosphorus of commerce is obtained by the decomposition 

the hones of animals, which constat largely of calcium 

phospli P'm. The hones arc tir>t burned, and, 

the organic matter being consumed, the ash is redaoed to 

deed in oonoentrated Bnlphnrie acid. This 

lompoees the phosphate, with the formation of insoluble 

cium sulphate, ami soluble arid calcium phosphate 

. H 4 1\.< >•)« The solution of this com pound, after being 

srated from the sulphate, evaporated to rirupy consist- 

-•, mixed with ehareoal, and dried in an iron pot, is 

distilled at a bright-red heat. The carbou unites with the 

, liberating the phosphorus, which rises in rapor, 

and is condensed in water in the Bhape of yellow drops. 

These, after having become solid, are melted again under 

the liquid is then forced into tubes, thus forming 

the ordinary st iek-phosphorus. 

248. Properties. — Phosphorus is a colorless, or faint- 
yellow, half-transparent, waxy solid. When exposed to 

il under wat.-r.it gradually becomes white, opaque, and 
scaly. Exposed to direct sunlight underwater, phosphorus 

antes covered with a red coating, and the none modifi- 
is formed when ordinary phosphorus is heated to i 

C\, in a pis w hieh ha> no action 

upon it. I: is extremely inflammable, taking fire in the 
d air by the slightest friction, and burning with great 
nutting a brilliant flame 
of phosphoric pentoxide. If quietly exposed to the air, it 
undergoes slow oxidation, emitting s bite vapors of s garlic 
ihines in the dark, wheno me, phosphoi 

It must be bandied with caution, as the 
hums it produces i and difficult to heal. It m. 

14 C, forming an oily liquid. 1 1 ount of it- in- 
inmability it is kept and cut under I 

alcohol and ether. ! 
beet solvent ion disulphide. Pram I ■ it 

lises in Conns of th< rdinarilj in 




138 DESCRIPTIVE CHEMISTRY. 

rhombic dodecahedra (Fig. 80). Phosphorus is a violent 
poison, and therefore frequently used for destroying ver- 
min; but it also serves as an external 
and internal remedy. The proper treat- 
ment for poisoning by this substance is 
to remove the phosphorus from the 
stomach by a stomach-pump, or, if it has 
been swallowed some time, by an emetic. 
Some thick gruel containing chalk or 
Fig. so.— crystal of magnesia is then to be given. The chief 
use of this substance is in the manu- 
facture of friction-matches ; and vast quantities are con- 
sumed in this way among all civilized nations. 

249. Modifications. — The red modification of phos- 
phorus may be obtained by exposing ordinary phosphorus 
to sunlight, or heating it to near its boiling-point in an 
atmosphere free from oxygen. As thus prepared, red 
phosphorus, also known as amorphous phosphorus, is a 
red powder, not fusible, but reverting to ordinary phos- 
phorus when heated to 260° C. It exhales no vapor or 
odor, oxidizes but very slowly in the air, does not change 
oxygen into ozone, is chemically indifferent, may be han- 
dled with impunity, and is not poisonous. There is a 
third modification, called black or metallic phosphorus, 
which is produced by heating ordinary phosphorus with 
lead in sealed tubes. When red-hot it dissolves in the molt- 
en lead, and in cooling separates in black rhombohedra, 
of metallic luster, which may be obtained in a pure state by 
dissolving the lead in dilute nitric acid. Phosphorus 
forms three compounds with hydrogen, but only one is of 
importance to the student. The process of its formation is : 

3KOH + P 4 + 3H 2 = PH 3 + 3KH 2 P0 2 . 

250. Compounds with Oxygen. — There are four oxy- 
acids of phosphorus, and the anhydrides of two of them 
are known : 



BED PHOSPHORUS. 



L39 



Pl)08] ihytlri.lr. 

anhvtlr 



Bjpophosphor 

sphorotu m id, 1 1. 1'< > 3 . 
Phoephorio acid, II,P< v 
Bypophoephoi ic acid, HJ'< >,. 

PI '.II PO* may be extracted from bone- 

ash, and can also be prepared bj treating phosphorus 
with nitric acid. Phoephorio and hypophosphorona acids 

arc entirely harmless, while phosphorous aci.l is a fioleni 
••n. 

When phosphorus La burned in dry oxygen (Pig. Bl), 
the thick, white vapors which are formed condense apon 
in snow-like Bakes, 
phosphoric pentox- 
phosphoric anhv- 
dri<: It has a pow- 

erful attraction f«>r moist- 
ure, absorbing it from the 
:* broughl into eon- 
with water. Beixing it 
with sneh violence as t<> 
emit a hi mcL 

By boiling it- solution in water the pentoxide ifl oon- 
into normal or ortho-phosphor •' (II PO 

ire three phosphoric acids, differing in the quantity 
«»f HfO which they hold in combination, in basicity, and 

in thru !is: 

P f | 3H,0 = -MI PO* Ortho-phoephori 
P f • 2H,0 IM\<> . Pyro-phosphoric acid 
: 8HP0 , &f< la-phosphoric acid 

Pbospl iom with chlorii 

, which, by the action of • 

it II P0 4 and 1 
251. Use of Red Phosphorus Ajnorpk 
ph ;tt present manufii 

for the pn-j.it .. which mav bo 







140 



DESCRIPTIVE CHEMISTRY. 



handled without danger of poisoning, or of lighting by 
accident. The ends of the matches are dipped into a 
paste of potassium chlorate, antimony sulphide, and gela- 
tine solution. One side of the match-box is coated with 
a mixture of red phosphorus, powdered glass, and gelatine 
solution. The match will light only when it is scratched 
upon this composition. Phosphorus, in this case, only 
serves to increase the oxidizing effect of potassium chlorate 
on antimony sulphide, induced by the heat of friction. 

252. Phosphureted Hydrogen (H 3 P) {Hydrogen Phos- 
phide). — This is a colorless poisonous gas, of a very offen- 
sive odor, like that of garlic. It is found in nature, 
being produced sometimes in small quantities by decay of 
animal matter, and appears to be the cause of the Will-o'- 
the-wisp. It may be prepared by heating small fragments 
of phosphorus with a strong solution of caustic potash, 
or with milk of lime, in a retort. The end of the retort- 
tube dips beneath water, and as the gas passes out in bub- 
bles, it rises to the surface, where each bubble burns spon- 
taneously with a flash, producing a ring of smoke (Fig. 

82), consisting of 
phosphorous pen- 
toxide. If some 
pieces of calci- 
um phosphide are 
thrown into a glass 
of water, the same 
thing takes place. 
Double decomposi- 
tion with the water produces phosphureted hydrogen, 
which ignites on contact with the air (Fig. 82). Pure 
phosphureted hydrogen (H 3 P) is, however, not spontane- 
ously inflammable, this property being due, in this case, to 
the admixture of a minute quantity of a liquid compound 
(H 4 P 2 ). The atomic weight of phosphorus is 31 ; while 
the specific gravity of its vapor has been found to be 




Fig. 82.— Wreaths of Flame. 



ARSE 



111 



KM, The volumetric composition of hydrogen phosphide 
will be readily understood by reference bo the sooompany- 



H 
1 








11 
1 


• + 


= 


PH M 








II 
1 






g 3, . Irsi nic* 



t>ol, A?. Atomic v. lantiralence, III tod V, Specific 

253. Arsenic. — This element is found native, lm t most 

ommeroe is obtained by the deoompo- 

■»n of the arsenides, or compounds of arsenic, with 

cially iron, cobalt, and nickel Tin are 

heated in retortfl of earthenware; the arsenic sublimes 
and collects in iron tubes and earthen rcceiv. 

Arsenic appears cither in steel-gray rhombohedra or 
as an amorphous black mass. The coarse, gray powder, 
sold under the name of u fly-poison," or M oobalt,"is an 
impure arsenic, i of its property 

iN. When arsenic is heated in a do 

1 /ilizes without fusio I a del 

ing th<- peculi md 

rresponding to the formula As* If heated in the 0] 
air it takes tire, burning with a blue flame, with torn 
ic trioxide. It is highly poi 

254. Arseniureted Hydrogen ill lr- 
*eni<l* ). — This gas may be formed I 

with dilute sulphuric m id, or 



142 



DESCRIPTIVE CHEMISTRY. 




by introducing a solution of arsenic into a flask in which 
hydrogen is being evolved. Arseniureted hydrogen burns 
with a bluish- white flame, is highly poi- 
sonous, and of a disgusting odor. It is 
in the form of this gas that arsenic is 
detected by Marsh's test. Fig. 83 shows 
an apparatus which answers, in a rough 
way, for this purpose. Bits of zinc and 
a little water are placed in the bottle, 
which is provided with a cork through 
which a tube is inserted. Sulphuric acid 
is now poured in through the funnel- 
tube, and the evolution of hydrogen com- 
mences. After the air has been corn- 
pletely expelled from the flask, the gas 
may be lighted at the jet. If the solu- 
tion containing arsenic is poured in 
through the funnel-tube, the color of the flame soon 
changes, and a cold, white surface, such as a porcelain 
plate, held so as to cut the flame in half, is stained with 
a black or brown spot by the deposition of arsenic. An- 
timony produces a similar effect, but a solution of calcium 
or sodium hypochlorite dissolves the arsenical stain, leav- 
ing that made by antimony unchanged. In practice, 
where much depends upon the evidence of even the 
smallest traces of arsenic, the gas before leaving the ap- 
paratus is made to pass a tube filled with pieces of cal- 
cium chloride, which retains all the moisture carried off 
by the gas. In presence of water a part of the arsenic 
by oxidation escapes notice. This is a very delicate test, 
but great care should be taken that the sulphuric acid and 
zinc do not contain any previous traces of arsenic. It is 



Fig. 83. — Marsh's 
Test. 



estimated that 



70000 



of a grain of arsenious oxide in one- 



hundred-grain measures of the solution may be detected 
in this way. The process is explained by the equation : 
As 2 Zn 3 + 3H 2 S0 4 = 2AsH 3 + 3ZnS0 4 . 



AKSKNIC OXIDES \M» Aiil 1 [:) 

The operator has to guard against inhaling the gas, which 

ions. (»reen colors of wall-papen fre- 
quently contain arsenic, ami arc injurious to health, giving 
off hydrogen arsenide in moist air. 

255. Arsenic Oxides aid Acids (As,O a ) [Arsenic 7W- 

. -This compound occurs native, hut is also prepared 
on a large scale by roasting certain ferric arsenides, and 
Oth- -. Thus obtained, it constitutes the 

Well-known white arsenic or ratsbane of commerce, a 

whi . capable of existing in three isomeric 

forms. By sublimation of common white arsenic a trans- 
parent amorphous mass, resembling glass, may be obtained, 

whi | by erv>talli/.ati<»n, becomes milky, like poi 

From itfl Solution in hydrochloric acid it separ.i 

in regular ootahedra, which shine in the dark. The or 
tals formed from its cooling rapor are rhombic prisms. 

It is soluble in about ten parts of hot water, the BOlution 
baring a slightly sweetish taste, and acid reaction. It 
alse < readily in hot hydrochloric a<id, and in solu- 

tions of the alkaline arsenit.s. It is used in dyeing and 

calico-printing, in glass-making, and f«>r the preparation 

of arsenical soap, which is employed for preserving stuffed 

I. Though a violent, used in 

: etTeetual antidotes are the moist hv- 

drated ferrie oxide and caustic magnesia. .1/ 
( II. formed by oxidizing arsenious oxide by tnei 

id. It has strongly acid properties, <\<><> mpos- 

256. Sulphides of Arsenic. 1/ ^ilfhuh 

is bond native as realgar, a mineral crystallising in trai 
. oblique, rhombic prisma, of beaatiful i 

. oolor. It ii produ -od 

as s in the fire-worki known a- M I'.mgal 

. familiarly known 

as- -it," ifl found native, but II slSO 'ti- 

dly. It is a bright-yellow isi d in 



144 DESCRIPTIVE CHEMISTRY. 

dyeing to reduce indigo, and also in the preparation of 
" rusma," a paste employed to remove the hair from skins. 
Nearly all the compounds of arsenic resemble those of 
phosphorus in form and properties. 

§ 4. Antimony. 

Symbol, Sb. {Stibium). Atomic Weight, 120; Quantivalence, III and V; 
Specific Gravity, 6'V. 

257. Antimony is found native, though most of the 
commercial supply is obtained from the trisulphide (Sb 2 S 3 ), 
the mineral stibnite. It exists in two modifications ; ordi- 
narily it is a brittle, brilliant, bluish -white substance, 
crystallizing in rhombohedrons. Amorphous antimony, 
the other form, is obtained by electrolysis, of very concen- 
trated solutions of its salts. When struck or heated it 
suddenly reverts to the crystalline form with evolution of 
great heat. Antimony melts at 450° C, and vaporizes 
at a white heat. It burns in the air with a white flame. 
Antimony resembles the metals even more than arsenic 
does. Unlike most substances, it expands at the moment 
of solidifying. Hence it is added to many important 
alloys to give them this property, which enables them to 
fill all the lines and crevices of the mold in making cast- 
ings. One part of antimony is mixed with 1 part tin and 
2 parts lead to make type-metal ; with 9 parts tin to make 
Britannia metal ; and with 12 parts tin and a little cop- 
per to make a variety of pewter. 

258. Compounds with Oxygen. — The composition of 
the oxides and oxyacids of antimony is similar to those 
of phosphorus. Antimonious Oxide (Sb 2 3 ) (antimony 
trioxide) is produced when antimony burns in the air. It 
is white (yellow when hot), crystalline, and almost insolu- 
ble in water. It occurs as a mineral, and is called white 
antimony ore. It is sometimes used in place of white- 
lead in making paints. Antimonic Oxide (Sb 2 5 ) (anti- 



;,,N 1 us 

lb white when oold Mid yellow when 

■:h in water and in acids. By add- 
: the elemen ater to these oxi uk acids arc 

ie<L 

259. Chloride of Antimony.— .!/////// Chloridi 

;tter of antimony) is a soft, crystallizahle, deli- 
quescent solid, soluble in a little water, bul 
ompoeed by a large quantity. It is used for bronzing 
prevent their rusting, and aa a caustic 
Antimonic Chloride (SbClf) ta a colorless, faming Liquid, 

uinir odor. It is used in the laboratory 
a 8or , which it gives ofl very readily. 

260. Sulphides. — Antimony forms an antimonioua and 

inlphide corresponding in form to the two 
The former, or trisulphidt >ura native 

as tin* gray, Bhining mineral Btibnite (gray antimoi 
When formed from solutions of other antimony salts, it 

. bat tn . when heated. It is u>i><\ in 

terinary medicine, for vulcanizing robber, in making 
safe hea and fire-works. The pentasolphide is an 

-yellow solid, which is decomposed by heat 

Boron, 

8jmbol, B. Atomic Wcitrht, 11; Qu;intivalen- , III; S rav- 

261. Boron. — This I found native, but 
may be prepare : >n oxide | 1 >. ( I | 

th sodium or aluminum. When prepared with .-odium 

>wn, amorphous, and maj 
i by nitric acid. Crystalline boi 
ii aluminum, exhibits almost oolorlesa octahedra of 

brilliant ingly hi 

stamlii Liamond in * 

262 Boric Acid, II I: 

.••nt of hot mi:. pd 



146 



DESCRIPTIVE CHEMISTRY. 




- ■'^$1^ ,. 






"''"' '''*' ' 



-v. rap 



locality being the 
" lagoons " of the 
volcanic district of 
Tuscany, where the 
acid issues from the 
earth with jets of 
steam, and is col- 
lected by conduct- 
ing the jets into 
water (Fig. 84). 
The acid is after- 
ward separated 
from the water by 
evaporation in lead- 
en pans, so arranged 
that they are heated 
by the vapors as 
they escape from 
the earth. It is 
deposited in white 
hexagonal crystals, 
which are purified 
by repeated crys- 
tallizations. These 
crystals have a 
glassy appearance, 
and are soapy to the 
touch. They dis- 
solve much more 
readily in boiling 
than in cold water, 
and form a solution 
having feebly acid 
properties. The 
presence of boric 
acid in a liquid or 



BORON 0OMFOUND& 117 

solid substance may be ascertained in several ways. The 
L when liberated by another arid, may be dissolved by 
>hol, which, when ignited, will burn with a green Same. 

Kil- . immersed in tincture of turmeric, and then 

dried, when brought into solutions containing boric acid, 
- from yellow to brown. It i\*>r> the Batne with all 

alkaline liquids, but with the difference thai the brown 
-r produced by tin* latter disappears by adding an acid) 

while tl caused by boric acid undergoes no change* 

263. Boron Trioxide | IV.o,). — This compound, the an- 
Iride of boric acid, is produced by subjecting the acid 

. whereby it loses its water : 

SHaBO = 3H,0 + 1V,(),. • 

264. Sodium Tetraborate | S . 10H t 0) ( Borax).— 

This sail is found native at the bottom of certain la 

in Thibet and California. It is procured artificially by 

iting boric acid with sodium carbonate, decomposition 

taking place with evolutioi irbon dioxide. Borax 

has an alkaline 1 reaction, and in the Fused si 

thigh heat, possesses the property of dissolving many 

ides ; h< a flux in solder:' 

ling metals. It dissolves the coating of oxide formed 
win heated, which thus constantly j 

sen* ( I nt ot the same proper! 

is one of the mosl importanl reagents in blow-pipe analy- 
->. r ameling, to make the enan 

. colors on porcelain, in gls 

ware, and in medicii 



148 DESCRIPTIVE CHEMISTRY. 



CHAPTER XV. 

BIVALENT NON-METALS — OXYGEN, SULPHUR, SELENIUM, 
TELLURIUM. 

265. The elements of this group, with increasing 
atomic weight, exhibit higher and higher specific gravity, 
melting and boiling points, together with a growing re- 
semblance to the character of the metals. 

§ 1. Oxygen. 
Symbol, 0. Atomic Weight, 16 ; Quanti valence, II ; Specific Gravity, 1*1; 

266. Oxygen. — This element is known to us in two 
modifications. The form commonly called oxygen has a 
molecule apparently made up of two atoms (0 2 ), while the 
other modification, ozone, is believed to have three atoms 
in its molecule (0 3 ). Oxygen gas was discovered in 1774, 
by Dr. Priestley, and the following year it was discovered, 
independently, by Scheele. Its discovery was also claimed 
by Lavoisier, who, in 1781, gave it the name oxygen, from 
two Greek words, meaning acid-former. This has been 
justly pronounced the capital discovery of the last century, 
rivaling in importance the great discovery of gravitation, 
by Newton, in the preceding century. It formed one of 
the great eras in the progress of human knowledge ; it put 
an end to old theories, laid the foundation of modern 
chemical science, and furnished the master-key by which 
man has been enabled to open many of the mysteries of 
Nature. 

267. Of its vast practical consequences, Prof. Liebig 
observed : " Since the discovery of oxygen, the civilized 
world has undergone a revolution in manners and cus- 
toms. The knowledge of the composition of the atmos- 
phere, of the solid crust of the earth, of water, and of 
their influence upon the life of plants and animals, was 



OXTGra [49 

(ink liseovery. The sueeessful pursuit of 

innumerable trades and manufactures, the profitable sepa- 
ration <>f metals from their on stand in thecloc 

nnection therewith. It may well be said that the mate- 
rial prosperity of empires has increased manifold since 

time oxygen became known, and the fortune of every 
individual has heen augmented in proportion/' 

268. Occurrence. Ow gen ia the most abundant and 
lely distributed element in nature. It forms two 

ninths by i f the atmosphere, and eight ninths of 

water; it is a chief constituent of the most abundant 

minerals, forming fully one half of the solid crust of the 

re than half the substance of all growing plants, 
nearly three fourths of that of animals, is oxygen. 

269. Preparation. i may he procured in many 
M.Tourio oxide and niamranese dioxide readily 

yield it when they are expose. 1 to a high temperature. It. 

can be obtained in large quantity, and very pure, from 

• ISSium chlorate. Fourteen grams of the salt are 

<'d in a isle, which ia fitted tightly with a cork, 

ass tube, bei to dip under the shelf 

gh ( Kg, The flask is heated, 

and the eli! more than a third of its weight 

gas. T iinn, chlorine, and 

I in the change the whole <>f the oxygen ta d 

engaged, potassium chloi laining hehind. 

8KC10, = 2KClH 

i> much facilitated 
miTing with -f cuprio oxide, 

iganesc roughly dried. These sub 

e no acti the ch lid the 

270. Properties I I less, in- 
TOU8 pi rier than air, and 16 tie 



150 



DESCRIPTIVE CHEMISTRY. 



at a temperature of — 130° C. it is converted into a color- 
less liquid. Oxygen is slightly soluble in water, 100 




Fig. 85.— Generating Oxygen Gas. 

volumes of which absorb about 4^ of the gas. Although 
apparently the very type of passiveness, this substance is 
endowed with the most intense power. The two atoms, 
which together form a molecule of oxygen gas, are held 
by but feeble attraction, and are easily separated, where- 
upon they enter into new and firmer combinations. 

271. Combustion in Oxygen. — All combustion in the 
open air is the result of the action of oxygen. It has a 
powerful affinity for the elements in 
fuel, and unites with them with such 
violence as to give rise to the heat 
and light of our ordinary fires. All 
substances which burn in air, burn 
in pure oxygen with greatly increased 
brilliancy. If the flame of a taper 
(Pig. 86) is extinguished, and a sin- 
gle spark remains upon the wick, on 
plunging it into a iar of pure oxygen 

Fig. 86—Taperm Oxygen, f Jj f J * J& 

it will be relighted and burn with 
extreme vividness ; and this may be repeated many times 




COMB! STION I\ <>\^ 



LSI 



in the * .<• r.»inl>u>tinn <.f ;t splinter 

3 brilliant! and a piece of charcoal glows and 

in the most beautiful mann< 

a usuallj Incombustible also burn 

1-iitlv in ( of One iron \\ ire into 

• iral, and b a 

hit • D that b 

ipped in me 
phur to end. 

lighting . and 
Bpiral » 
jar he iron 

hams with dan 
brill ¥t i. 

:li" jar 
red with 

of 
whil iron from 

fusing into thi 

If a jar of OX] 

on which tJ. burning sulphur, a beautiful 

in the 

! urned 

in the same maimer, a blind- 
of light ia ( I 

mpanied bj 

i. In all th( 

imply U) 

the union of b the 

I 

... 
i 



i 

f i 





' 











152 DESCRIPTIVE CHEMISTRY. 

272. Oxidation in Nature. — Decay in vegetable and 
animal substances is produced by the action of oxygen, 
which breaks them up into simpler and more permanent 
compounds. Oxidation is also the grand process by which 
the earth, air, and sea, are purified from contaminations, 
noxious vapors and pestilential effluvia being destroyed by a 
process of burning — more slow, indeed, but as real as if it 
took place in a furnace. This slow combustion was named 
by Liebig eremacausis. The offensive impurities which 
constantly flow into rivers, lakes, and oceans, as well as 
the decaying remains of the creatures which inhabit them, 
are constantly being oxidized by the dissolved gas. In 
this way waters that have become foul and putrid are 
purified and sweetened by exposure to the action of air. 
This effect, however, is largely dependent upon the presence 
of ozone. 

273. Relation of Oxygen to Life. — Oxygen is the uni- 
versal supporter of respiration, and hence, as this is a 
vital process, it is the immediate supporter of life. From 
this circumstance it was first known as vital air. An ani- 
mal confined in a given bulk of common air, having con- 
sumed its oxygen, dies. If immersed in pure oxygen, it 
lives longer, but the effect is too stimulating — overaction, 
fever, and in a short time death, are the result. As the 
introduction of oxygen into the body is indispensable to 
animal life, the mechanism of all living beings is con- 
structed with reference to this fact. The lungs of the 
higher races, the spiracula of insects, and the gills of 
fishes, are all adapted to the same purpose — the absorption 
of oxygen, either from the air or water. The animal 
organism is chiefly composed of combustible constituents, 
and we introduce this wonderful element incessantly from 
birth to death, that it may perform its chemical work. 
The animal body is an oxidizing apparatus, in which the 
same changes occur that take place in the flame, only in a 
less intense and more regulated way. Every organ, mus- 



OBONE. [58 

md membrane, is wasted away, burned to poi- 

s and ashes, and thrown from the s\stem as 
uui dangerous matter. If these constant losses arc 
not repaired by a due supply ^\' \\uu\ % the consequen 
are emaciation, decay, and finally death. Starvation is 
thus nnimpeded oxidation —slow burning to death. 

274. Ozone (O t ). WTien electric sparks are pat 
throngfa dry air, a peculiar odor is perceived, which has 

died the M electrical smell." There was much doubt 
about the • it, until the investigations of Schdn- 

! that it was due to an allotropic form of OXy- 

I n»m the peculiar odor, its discoverer named it ozone. 
In nature this modification of oxygen is found principally 
during and after thunder-storms; hut the quantity con- 
tained in the atmosphere varies considerably, and i^ 

dl. Winds blowing from the sea contain more of it 

than those which sweep over large tracts of land, because 
it is usually formed where great quantities of water are 
The best method <.f preparing ozone is by 
the passage of eh-ctricity through damp oxygen. Several 
forms of apparatus called ozonizers have been invented 

for this purpose. Also when a spiral 
of platinum wire is heated in air, or 
When the air acts upon turpentine 
and some other essential oils, ozone 

1 . if we place a little 

md then in- 
troduce into it- vapor a moderately 
heated glass n id (I 

! rich i 
v prepared by mix- 

tassiutn perman, a ith cold, ttl- 

phuf 

275. Properties. In most of its physical p 

the ordinary modifl 

a bluish tint, for, when 




154 DESCRIPTIVE CHEMISTRY. 

it forms an indigo- colored liquid. It differs from oxygen 
in possessing a powerful odor, somewhat resembling dilute 
chlorine gas. It is slightly soluble in water, more readily 
in ether and essential oils. The most remarkable prop- 
erty of ozone is its powerful oxidizing action. In fact, 
it is oxygen greatly intensified in activity. It corrodes 
metals upon which ordinary oxygen does not act, for ex- 
ample, silver ; it quickly bleaches colors, which are com- 
paratively permanent in the air ; it deodorizes tainted 
flesh, destroying its effluvium instantly, and carries woody 
fiber in a short time through a course of decomposition, 
which, with common oxygen, would require years. It de- 
composes potassium iodide, setting the iodine free. Free 
iodine combines with starch, turning it blue ; therefore, a 
test of ozone is made by soaking slips of paper in a mixt- 
ure of starch and potassium iodide. The slightest trace 
of ozone immediately turns it blue. Prepared paper, ex- 
posed for a few minntes to the open air, will frequently 
turn blue, which is supposed to be due to the presence of 
ozone. It is probable that it is generated on a large scale 
in the atmosphere, and that it serves an important pur- 
pose in the economy of the globe as a purifier of the air, 
and hastener of decay. Ozonized air irritates the respir- 
atory organs, and a minute quantity kills a rabbit. At a 
temperature of 300° C, ozone is reconverted into ordinary 
oxygen. This substance is used for bleaching discolored 
engravings. 

It was supposed for a time that there was a third modi- 
fication of oxygen, which was called antozone, but it has 
since been proved that the effects ascribed to it were due 
to hydrogen dioxide. 

276. Water (H 2 0) {Hydrogen Oxide),— Of the im- 
portance of water in the economy of Nature little need 
be said ; it is obvious to all. It is the most abundant sub- 
stance that we know, and it seems as if the whole scheme 
of Nature were conformed to its properties. Turning to 






. 

i obe. B om 

tlu- apoD the land, and Bowing bach 

aga -n in its circulation the grand 

• ostituting four fifths the weigh! 
. and three fourths that of the 
lition of all organization, and 
tmerable >rmations and decompositions it is 

essential to the continuana mic lifa Nor is it 

le in tin . where il 

a thousand operatj 
and takes part in many chemical reactii 

277. Production of Water. — If hydrogen is genera 
in a jar and allowed to _ . fine tul 

ns, when ignited, with 
ing ou1 but little 
gh producing in it. In all 

cases where hyd 
wat product I 

red wit! 
film dch rapidly incr 

of water. The gaa 
whirh t: ato the liqui 

burn quietly when 
>usly in »nt, if the 

gases an- i rition, in th< 

ad, a rioleni explo- 
. blown with this mixture from 
a bag a 

278. Composition. \\ 

I 
: of hydrogen. ! 
i\\-, but 

The m< b 




156 DESCRIPTIVE CHEMISTRY. 

drogen free with such violence as to produce the vivid 

combustion of the latter (Fig. 92) ; the water seems set on 

fire. Water is also decomposed by 

m sodium, iron, and zinc, and many 
In numberless operations of 
chemistry, the elements of water 
are separated and reunited, and the 
same thing is going on perpetually 
in vegetable and animal organisms. 
~ ^^Tzz^Erz --r^ But the composition of water may 
fig. 92. — DecomposiDg be shown in the most perfect man- 
ner by sending an electric current 
through a vessel of it (Fig. 43), as already described (93). 
The gases are set free in the exact proportions given 
above, and, if mixed and ignited, they combine with a loud 
and sharp explosion, the product being pure water. The 
composition of water is thus demonstrated by both analy- 
sis and synthesis. 

279. General Properties. — Pure water is a transparent, 
tasteless, inodorous liquid. It is but very slightly con- 
densible by pressure, and is perfectly elastic, as it regains 
its full dimensions when the pressure is removed. It 
evaporates at all temperatures ; boils at 100° C. or 212° F., 
and freezes at 0° 0. or 32° F. The vapor given off by 
water has a pressure which is resisted by the pressure of 
the atmosphere. When, by an increase of heat, the ten- 
sion or pressure of the vapor becomes equal to the pressure 
of the atmosphere, the liquid boils. It follows that, if the 
pressure of the air is reduced, water will boil below 100° C, 
and, if the pressure is increased, it will not boil till it 
reaches a higher temperature. It is 815 times heavier 
than air. The weight of one cubic centimeter of distilled 
water, at 4° C, is taken as unity in metric weights, and 
is called a gram. The specific gravity of water at the 
same temperature, which is its point of greatest density, 



SNOW-CRYSTALS, 



157 



d adopted as the unit for Bolida and liquids. In 
tin , but light passed through tlf- 

:' pure water emerges of a bright and delicate 
. and, by augmenting the thickness, the coloi 
pened. 

280. Snow-Crystals. — Water, in freezing, crystallizes in 
the hexagonal Bystem. The aqueous vapor of the atmos- 
phere, condensed by cold in winter, and at great heights 
in summer, assumes the most beautiful crystalline forms 
— i mow-flakes. Perfect snow-flakes are six-pointed 

stars — modifications of an hexagonal prism— which Bhoot 
• an infinity of delicate needles, all diverging from each 
other at an angle of 60 . These frozen Mossoms, as they 
hav aptly termed, are seen in an endless variety of 

Forms, a few of which are shown in Pig. 

When a ray from the sun or an electric light IS made 




.- 



Ui pass through a block of purr ice, a portion <>f the beat 
is arrested, and must, of course, produce change. As it 



158 DESCRIPTIVE CHEMISTRY. 

return to the liquid state in definite order, and, upon ex- 
amining it with a magnifier, the ice is seen to be filled 
with beautiful flower-like figures. These consist of water, 
but as the liquid formed can not quite fill the space of the 
melted ice, there occurs a little vacuum, which looks like 
a globule of burnished silver in the center of the flower. 

281. Unequal Expansion of Water. — This liquid con- 
tracts as its temperature falls from the boiling-point till it 
reaches 4° C, when it begins to expand, and, in cooling 
to the freezing-point, it reaches the same volume it had 
at 9° C. The point of greatest contraction, or the point 
of maximum density of water, is thus 4° above the tem- 
perature at which the liquid solidifies. The presence of 
dissolved salts, as in sea- water, lowers the point of maxi- 
mum density. This fact is of great importance in nature. 
If water continued to contract as it cooled, it would 
be densest and heaviest at the freezing-point, and would, 
consequently, sink. Lakes and rivers would then freeze 
at the bottom first. In the course of the winter they 
would become solid masses of ice, and the length of time 
required to thaw them would greatly prolong the cold 
season. But as the surface layer of w T ater approaches the 
freezing-point it expands, and, becoming lighter, floats, 
and in crystallizing or freezing it expands still more, ten 
volumes of water forming eleven volumes of ice. Thus 
the coldest water and the ice are kept at the surface, where, 
as they are almost perfect non-conductors of heat, they 
protect the mass of water below from the cold air above. 
In freezing, water expands with such power as to burst the 
strongest vessels. Percolating the minute crevices and 
fissures of rocks in summer, it freezes in winter, and ex- 
pands with a force which breaks the solid stones, crum- 
bling them into soil fit for the support of vegetable life. 

282. Its Specific Heat. — The specific heat of water is 
four times greater than that of air ; that is, a pound of 
water, in cooling one degree, would warm four pounds of 



:.\ t\t vow i;k Of WAT\ [59 

air 315 times heavier than 

air, it is obvioofl that a cubic fool ol water, in cooling i 

lid warm ft>UT t inns 815 Cubic feel "t" aii. 

Thus it ia a powerful agency 
vasl amount of heal Btored up 
in i dually imparted to the air 

duri rerity of the cold, and ex- 

plai fact that island winter.- air Less Bevere than 

r inland pla 
Th' ability ot Nature seems to depend upon this 

dity oi the earth's aqueous element. If the wab 
-es of the irlo! . U as that contained in our own 

[aired heat as promptly as mercury, the 
!n temperature would he inconceivably m 
rapid than now; the inconstant seas would ' and 

thaw with I Facility, while the slightest chanj 

ther would Bend their fatal undulations through all 
Uvi Bui now the large amount of heal accu- 

mulated in r during summer is given oul 

v and i! I rate: the climate is tempered, and 

from h( 1 are graduaL 

283. Its Solvent Power.— Water the power 

dissolving many .-olid, liquid, and ■_ substant 

- with difl substances, and 

a di tTerei it trin j % Thus, a pound of cold wai 

will disc • sugar, while it will only take 

up - , two of alum, or eight 

ally increases the Bolvenl pc 
. thus boiling water n ill 
nui 

afl much lime as boili 
water. A 

. 

<.f the Uqui *u- 



160 DESCRIPTIVE CHEMISTRY. 

solution is one which has taken up all of the substance to 
be dissolved that it will hold. Such a solution may still 
be capable of taking up a quantity of a different substance. 

Liquids which will mix with water, as alcohol, are said 
to be soluble in it. The liquid of which the larger quan- 
tity is present is generally spoken of as the solvent. 

Water dissolves gases in the most diverse proportions, 
taking up, at 0° C, more than 1,000 times its bulk of am- 
monia ; about twice its bulk of carbon dioxide ; -^ its bulk 
of oxygen, and scarcely -^ its bulk of hydrogen. There 
is, therefore, an atmosphere diffused throughout all natu- 
ral waters, which is richer in oxygen than common air, 
and hence better adapted for supporting the life of aquatic 
animals. The gases absorbed by water give it a brisk, 
agreeable flavor, and, if driven off by boiling, the liquid 
becomes insipid. The solubility of gases in liquids in- 
creases as the temperature decreases ; it also increases with 
pressure. 

284. Varieties of Water. — Water never varies in chemi- 
cal constitution, but its usefulness is often affected by 
substances dissolved in it. Rain-water is comparatively 
pure, but in falling to the earth it always takes up more 
or less of the common salt, organic matter, ammonia, 
nitric acid, etc., which float in the air. These impurities 
are largest in amount in cities and near factories. The 
rain-water which falls after it has been raining several 
days, so that the atmosphere has become well washed, is 
the nearest approach to pure natural water. 

The water of surface streams and lakes is rain or snow 
water which has been in contact with the rocks and soil, 
and may contain soluble substances in solution, and also 
more or less of insoluble matters suspended in it. The 
quantity of solids present varies up to 200 grains or more 
in a gallon. Calcium and magnesium carbonates and sul- 
phates and sodium chloride are the salts oftenest found 
in water. Surface - water often contains much organic 



VAK1KTIKS OK WATER [ft] 

matter, rting ot vegetable and animal substao 

washeil or thrown into it. Many rivers are distinctly 

colored by the tine clay or other soil whieh the water holds 

in suspension. 

Water is ontinually filtering through loose soils, and 

ring through CTericefl and passages beneath the surface 

ground. Underground waters^ which come to the 

. Mr are pumped up through wells, are 

usually quite free from organic matter, hut contain a 

iter variety of mineral substances than surface waters. 

, ordinarily insoluble, the water is enabled to 

by the aid of its heat, or of the gases which are 

in the confined spaces which it past 

through. Many spring-waters are useful as medicine on 

DUnt <>f the salt- and gases which they hold in solution, 

died medicinal or mineral waters. They have 

also special nan ffding to the nature of their inedi- 

iraten contain carbonic acid 

. . ^ Apnllinaris, and the Saratoga water- 

contain magnesium sulphate (Epsom 
i or sodium sulphate (Glauber's salt) (.•. L r ., Epsom, 

. S idlitz) ; calcareous waters con- 
tain <alcium sulphate, or calcium carbonate held in solu- 
. by the aid ot carbonic acid ; chalybeate water.- oon- 
bron ; alkalim waters contain sodium 
car 1 tnd bicai ;., Vichj hur wat 

1 hydrogen gas (a L r ., the Sulphur 

Minion sail 

- ill Lake, Dead Sea, and rarioi 
Many of these wa ther sub 

of chief impoi ''.'rent w 

for drinking <>r for bathing 1 me for both. Ann 

mineral wal te by di inary wa1 

arbon dioxide or other gases smh salts as 
i in the natural 

Sea-w<i f 



162 DESCRIPTIVE CHEMISTRY. 

magnesium chlorides, to which its bitter taste is due, also 
salts of calcium, and traces of bromides and iodides. 

Water which takes a large quantity of soap to make a 
lather is called " hard" This property is due to the 
presence of calcium and magnesium salts, a part of the 
soap uniting chemically with these substances and thus 
becoming useless. Temporary hardness in water is due 
to the carbonates of calcium and magnesium, which are 
soluble only so long as the water contains carbonic acid, 
and may be got rid of by boiling, when the carbonic acid 
is driven off, and the carbonates are precipitated. In 
boilers using such waters a crust is formed by the pre- 
cipitate on the inside of the boiler, called " boiler-scale," 
which causes a waste of fuel in heating the water, and 
scales off from time to time, letting the water come in 
contact with the intensely hot iron, much to the injury 
of the boiler. One way of preventing this deposit is to 
add to the water a little ammonium chloride ; ammonium 
carbonate is thus formed, which goes off with the steam, 
and calcium chloride, which, being soluble, does not form 
scale. Permanent hardness is due to calcium and mag- 
nesium sulphate, etc., and is not got rid of by boiling. 
Water is not made unfit to drink by moderate quantities 
of mineral salts, but when contaminated by any sort of 
filth it is very dangerous. 

285. Purification of Water. — Water, as found in Na- 
ture, is never perfectly pure, but always contains variable 
quantities of mineral and organic substances which are 
either held in suspension mechanically or are dissolved 
in it. It is also inhabited by myriads of minute living 
organisms known as infusoria. During freezing, the sub- 
stances dissolved in water are expelled. This is explained 
by the fact that, when the particles of any substance are 
crystallizing, particles of other substances do not unite 
in building up the crystals, except in cases where they 
crystallize in the same form themselves. Hence the ice of 



CHEMICAL PROPERTIES OF WATER 168 

sea- II known to Bailors), when melted, be- 

the Bame reason, water from 

mell tains nritluT air n<»r di ran not live 

in it. m method of purifying water is b) dis- 

tills to render it perfectly pure, it most be re- 

a low temperature, in silver \< » la By Bltra- 
., crushed charcoal, or other closely 
lia, water may be deprived of suspended impu- 
rities. Boiling kills all animals and tries, 61] 
gases, ami precipitates calcium carbonate. Two or three 
ins of alum to the quart is often used to cleanse muddy 
turbid water, but this does no! purify it, being merely 
posed by the calcium carbonate contained in the 

alumina set t'nv carries down the imjniri- 

Uy; hut the sulphuric acid of the alum, 
with the lime, forms calcium sulphate, and 
a the water harder than before. The alkal 

• ish, and Bod by decomposing and | 

oipj ,dts ; hut remain themselves in BO- 

httion. 

286. Chemical Properties. —All hough water is neither 
1 nor alkaline in its action OB ble Colors, ii is 

dly an exceedingly active body, inducing and and 
imposition when brought in contact with a 
:it substances. It unites with ba 
and with anhydrides to form 

. as sodium ear!, i\e off 

ordinary temperatui 
itassium carbonate, absorb 
the air, and di I teliqui 

i in the laboratory for freeing gases 

287. Hydrogen Dioxide (H,O f ) ii a tn 

less, strupy liquid, of l'i ity, which does 

I 

u ii in. It i m 



164 DESCRIPTIVE CHEMISTRY. 

posing barium peroxide suspended in water, by carbonic 
acid, 

Ba0 2 + H 2 C0 3 = H 2 O s + BaC0 3 , 

and by evaporation of the filtered liquid at a low tempera- 
ture. It has an astringent taste, a chlorine-like odor, and 
possesses active bleaching properties, due to its oxidizing 
power. It is a very unstable compound, decomposing 
slowly at 21° C, while higher temperatures, or the con- 
tact of various substances (powdered silver, platinum, or 
carbon), cause it to separate into water and oxygen with 
explosive violence. It may be regarded as free hydroxyl 
(HO), composed of two atoms of a compound monad rad- 
ical. Under the name "auricome" and "golden hair- 
wash " it has been used to bleach dark hair to a yellowish 
or " blonde " color. It is also used for bleaching oil- 
paintings and cleansing stained engravings. 

The Atmosphere. 

288. Its Composition. — It was not until the year 1777 
that Lavoisier pointed out the true composition of the 
atmosphere. Up to this time it was spoken of as one of 
the four elements ; but the careful observations of Priest- 
ley and Scheele, and their discovery of oxygen gas, pre- 
pared the way for a knowledge of its exact composition. 
It is now known to be a mixture of nitrogen and oxygen 
— the first incapable of supporting combustion or respira- 
tion, and the other essential to both. 

Stated in round numbers, the air contains by volume 
21 per cent of oxygen and 79 per cent of nitrogen ; by 
weight, 23 per cent of oxygen and 77 per cent of nitro- 
gen. Air is 14*45 times as heavy as hydrogen, and 815 
times lighter than water. A liter of air at 0° C. weighs 
1*3 gram. That the air is made up of these gases may be 
ascertained by analysis. That it is a mixture and not a 
chemical compound is shown by the facts that its compo- 



Tin; I mOfiPHBUB. 

nta are do! united in the ratio of their atomic weigh 
I that each gaa dissolves in water, independently of the 

other. But the analyses of air collected from ditTerenl 
parts of the earth, ami at different heights, show a iv- 
markahlc uniformity in its composition. 

289. Other Gases in the Air.— In addition to the oxy- 

and nitrogen present in the atmosphere, there is 

all proportion of the vapor of water, carhon 

dioxide, and ammonia. The proportion of watery vapor 

varies with the temperature. It usually ran ires from ^ to 

^ of the bulk of the air. A high degree of humidity 

in the air checks evaporation from the skin, causing a 
. " feeling, while if the air is too dry it takes moist- 

from the body 80 fast as to make the skin feverish and 
the mouth parched. 

By shaking up known quantities of air with a m< 
Died quantity of a solution »>f barium hydrate of known 

arbon dioxide is absorbed, and its propor- 
tion determined by neutralizing the remaining barium hy- 
drate with oxalic a. id <>f known itrength. It varies from 
partfl in 10,000 of air. It increases as we rise from 

the earth, and is less after a rain, which washes it down 
from the air; it increases during the night, and dimin- 
ishes after sunrise, is less over large bodiefl of water than 

r large tracts <>f land, and is m<»rc abundant in the air 

of towns than in that of the country. The carhon diozi 
in the air OOmefl from t!i i of animals and from 

In dwellings, school-houses, lactones, and 
rtion rangei froi in i".- 

00< than LO parts are present, the air do 

be regarded :l- impure. The carhon dioxide, which is 
poured into t! phere in prodigioui quantit 

from iniiun ••-arv to th 

rid as is oxygen to the animal irorhL U hod 

rtion, if it m 
withdr i •• world trould quickly perish* 



166 DESCRIPTIVE CnEMISTRY. 

Liebig has shown that the air contains minute traces 
of ammonia, which are washed down, and may be detected 
in rain-water. Traces of nitric acid have also been fre- 
quently detected. This substance is thought to be formed 
by electricity, every flash of lightning which darts across 
the sky combining a portion of the oxygen and nitrogen 
along the line of its course, and forming this acid. The 
saline particles from the ocean-waves, which are dashed up 
in foam and spray, are carried by the winds far inland. 
Particles of dust, germs of fungi, and other solid sub- 
stances float in the air, and are revealed when a sunbeam 
crosses a dark space. All these substances are brought 
down by the rains, and help to quicken the growth of 
vegetation. 

290. The Atmosphere and the Living World. — Each 
of the constituents of the air is essential to the present 
order of things. Oxygen is pre-eminently its active ele- 
ment. To duly restrain this activity, the oxygen is diluted 
and weakened by four times its bulk of the inert element, 
nitrogen. Their properties are thus perfectly adjusted to 
the requirements of the living world. Were the atmos- 
phere wholly composed of nitrogen, life could never have 
been possible ; were it to consist wholly of oxygen, other 
conditions remaining as they are, the world would run 
through its career with fearful rapidity : combustion once 
excited, would proceed with ungovernable violence ; ani- 
mals would live with hundred-fold intensity, and perish in 
a few hours. The relations of the atmosphere to living 
beings, the stability of its composition, and the wonderful 
forces that are displayed within it, are full of surpassing 
interest. The vegetable world is derived from the air ; it 
consists of condensed gases that have been reduced from 
the atmosphere to the solid form by solar agency. On the 
other hand, animals, which derive all the material of their 
structure from plants, decompose these substances by 
respiration, and when dead, their bodies putrefy, and thus 



-i i. nil R [Q7 

the mat I which they were buill ap arc returned in 

nee they came. 

S 

. II. IV, VI ; Sp 

291. History and Occurrence. — Sulphur is one of the 
oldest kn«' j- mentioned in the Bible, 

I in the writi the ancients. By the alchemists 

be the impurity in the base metals, and in 
tin- - ii was regarded as the principle of fire, 

substance being supposed to contain it. 
nndantly in nature. In the \'<>vu\ of crj stals or 
am found in various volcanic regions, 

as on the island of Sicily, where it is mined in immense 
II 1 with hydrogen as a gas in 

iften deposited in the fr 
rition of the gaa Sulphur-dioxide 
ga*= iled by volcanoes. Combined with the metals 

it fora a important and abundant orea (sulphidi 

I it is found united with the metals and oxygen in 
» <>f minerals (sulphates), some of which are 
I of many vegetable and ani- 

mal 

292. Preparation. — The sulphur of oomm< pre- 

the ini; form by simply melting the 

sol] I from i T - impuriti i e produ< out 

l\ btained 

tea, a sulphide of iron. T en- 

dim: the mineral with i 

on fire. A portion 
sulphide bui . by the of the h< 

remain im- 

posed * Iphur, i I utilizes and 

in the fluid 



168 



DESCRIPTIVE CHEMISTRY. 



surface of the heap. The following reaction represents 
the decomposition : 

3FeS 2 = Fe 3 S 4 + S 2 . 

Commercial sulphur is generally purified by a second 
sublimation, and reaches the market in two forms, due to 
the different modes of its preparation : first, as roll-sulphur 
or brimstone, obtained by running melted sulphur into 




Fig. 94,— Distilling Sulphur. 

molds ; second, as a pale-yellow gritty powder, flowers of 
sulphur, obtained by sublimation. A third form, milk of 
sulphur, is produced by the decomposition of solutions of 
certain sodium or potassium sulphides with acids. 

293. Properties and Uses. — Sulphur is a yellow solid 



MODIFICATIONS OF BOLPHUB \<\\) 

at ordinary temperatures, malting at llfi c. to 

Dow liquid. It has neither taste new odor. 1 iu- 

ble in water, bul soluble in alcohol and ether, 

. and a non-conductor of electricity. It 
slightly volatile at ordinary temperatures, 

. temperature ol from S 
t burns with a blue llama It combine* freely with all 

non-m< nitrogen, and with all the metals 

(many of which burn in its vapor) to form sulphides. In 

emical behavior it closely reeemMefl n, formi 

■unhides corresponding to basic and acid 

ed with positive radicals, sulphur is a dyad, but in 
other combinations it may be cither a tetrad or hcxad. 

- used in making friction matflhffl, in the 
manufacture of rubber and gunpowder, and as a Bource «»f 
;1 compounds. It is also used medicinally in sot 
•us of drin-diseae 

294. Modifications of Sulphur.— Sulphur, lik» 
is capable of existing in BOTeral modifications, differ 
in their y, melting- 

points,and solubility. The ordinary 
form is call- 

cans iaes in o< tahedr 

rhombic 

■areiit yelloi 
of sulphur which OCCUT in natur- 
of this form. T l>e regar 

as the normal modifl *" * ryiUU '- 

. f<»r they all past form 

rhombic sulphur Ifl m« 

raised to i riscid . 

on an osangi until, al thick to 

'. 
brown, a: I ajrain h 

black at 

///W.— 
8 




170 



DESCRIPTIVE CHEMISTRY. 




Fig. 96.— Crystals by 
Fusion. 



be obtained by melting ordinary sulphur in a crucible 
allowing it to cool until a crust is formed, then breaking 
the crust and pouring out the still fluid portion. The 
walls of the crucible will then be found lined with a mass 
of transparent yellowish-brown, needle- 
shaped crystals (Fig. 96), which are ob- 
lique rhombic prisms, or modifications 
of these. This form of sulphur has a 
specific gravity of 1*98, melts at 120° C, 
and in the course of a few days passes 
spontaneously into the ordinary octahe- 
dral modification. It is readily soluble 
in carbon disulphide. 
Plastic Sulphur. — This variety is produced by heating 
melted sulphur to a temperature of from 260° to 300° C, 
and then suddenly cooling it by pouring it in a thin stream 
into water (Fig. 97). It is a dark-brown, tenacious mass, 
which may be drawn into 
threads. It has a specific 
gravity of 1*95, and is in- 
soluble in carbon disul- 
phide. It gradually chan- 
ges to the ordinary modifi- 
cation. The plastic modi- 
fication of sulphur is often 
employed to take impres- 
sions of medals, coins, and 
similar objects. 

A luff amorphous va- 
riety remains undissolved 
after exhausting flowers of 
sulphur with carbon disul- 
phide. Its specific gravity is 1*95. The white variety is 
the amorphous form which exists in milk of sulphur. It 
is soluble in carbon disulphide. 

295. Sulphureted Hydrogen (H 2 S) (Hydrosulphuric 




Fig. 97.— Plastic Sulphur. 






SULPHURETED HYDRO 



171 



—This gas was discovered by Bcheele, in L777. I' 
.uiid abundantly in nature as a volcanic product, as the 
essential ingredient to which the vi I so-called sul- 

phur-springs owe their flavor, ami as one of the products 

iie dee;:. ..anie matter. It is UMiall J obtained by 

dphuric acid on ferrous monOBUl- 

phide. 

Fe8 + EaS0 4 = PeS0 4 + Il.s 

nvenient arrangement for its evolu- 
tion. The ferr<»us monosulphide should he broken into 
small lumps and placed in the 
flask. The cork and tubes may 

then he adjusted, ami first water, 
and then sulphuric acid pound in 

through the funnel-tube. The 

gas is absorbed by the water of the 

\d flask. The solution must 

in tightly-stoppered h<>t- 

posed to the air, it is 

gradually decomposed, becoming 

milk. aration ot finely 

divided sulphur: 

1I.S + n = H f + B 

296. Properties. -Sulphureted hydrogen is acoloi 
transparent gas, having the odor of I Oodledto 

— ! 1 ; at Hi' at 

10° ('., it condenses to a oolorl le liquid 

ty, which Creeses at I ion 

_- in the liquid. It readily dissohn 

ilution it- t.; m. -11. I 

taM : in the air it hi. 

with a pale-hli. If two folumes <>f it an- mi 

with three volumes mixture expl 

is highlj 
even when much diluted : l part in l.« .f air will kill a 










172 



DESCRIPTIVE CHEMISTRY. 



dog. Certain metals displace the hydrogen in the gas and 
form sulphides — some, as silver and mercury, even at ordi- 
nary temperatures. Silver- ware becomes blackened by this 
action, from the sulphureted hydrogen in the air, which 
comes mostly from the imperfect burning of coal that 
contains sulphur. Spoons are tarnished by this gas in 
eggs. Sulphureted hydrogen is used extensively in chem- 
ical operations as a reagent. Its action upon solutions of 
the metals may be shown by the apparatus represented in 
the accompanying cut (Fig. 99). The gas is evolved from 




Fig. 99.— Precipitation of Metals by Sulphureted Hydrogen. 



ferrous sulphide in a large flask, and passed through a 
bottle containing a little water, after which it successively 
passes through bottles containing solutions of cupric sul- 
phate, zinc sulphate, ferrous sulphate, and lead sulphate. 
The sulphate in the first bottle will give a black precipi- 
tate, that in the second a white, while the last two yield 
black precipitates. This action of sulphureted hydrogen 
is used in qualitative analysis for ascertaining the presence 
of salts of certain metals in a solution. The sulphides of 
different metals are distinguished by their colors, or their 
solubility in acids or alkalies. 



BULPHUB 00KPOUN1M9L 

297. Chlorides of Sulphur. — By | rv chlorine 
into melted sulphur, sulphur cfiloi S formed 
It is a yellow liquid with i pungent odor, and is used as a 
solvent for sulphur in the manufacture of fuleanised rub- 

Sulphur did - formed from sulphur 

chloride and chlorine; it is a deep-red liquid Both tl 
stances are decomposed by contact with watt 

298. Compounds with Oxygen. — Sulphur may unite 
wit b n ss a dyad, tetrad, or hexad. Chemists are 

[uainted with the following oxides and oxyacids of sul- 
phur : 

Hvposulphurous acid, II,SOt. 
B tphurous 8< } Sulphurous acid, Il. v<> . 

- llphuric oxide, SO,. Sulphuric acid, HJ9 

299. Sulphurous Oxide, EH >. | Sulphur D ).— This 
substance is one of the product.- of volcanic action, and 

always formed by the burning of sulphur in air, or in pure 

_ 

8, H-20 f = 2SO r 

It is a transparent, colorless gas of 8^8 specific gr a v ity, 
haying a pungent, suffocating odor, familiarly known in 
case of a burning match. The gas in: 

men! or over mercury. It extinguishes com- 
bustion; hence sulphur is often thrown into the tire to 
ench the burning soot of chimneys. Many fire-extin- 
n contain sulphur mixed with r I niter as 

kindlii _ rials. Air containing l pari in 10,000 de- 

str md if 5 parti 

It has I n f<>r water. Al- 

to escape* iii* ;r, it forms whil ■ with 

pre s en t, 
into the gai ly liquefied. Water ai kes 

up larir solution formed har- 

nicll of : f three 

aospheres at ordinal 



174 



DESCRIPTIVE CHEMISTRY. 



at 7° C, it condenses to a liquid which evaporates so fast 
that the cold generated will freeze water even in a red-hot 
crucible. At —76° C. it becomes solid. It reddens and 
afterward bleaches litmus. It is a powerful reducing agent, 
having a strong tendency to take up oxygen together with 
water to form sulphuric acid. 

300. Uses. — Sulphurous oxide is used to destroy para- 
sites and growths of mold, for bleaching silk, woolen, and 

straw fabrics, and taking fruit- 
stains and rust-spots out of 
linen (216). The goods are 
moistened and suspended in 
large chambers, or, in a small 
way, they are put into inverted 
barrels and exposed to the 
fumes of burning sulphur. 
The effect is produced, in most 
cases, not by destroying the 
coloring-matter, as in the case 
of chlorine, but by the union 
of the acid with the coloring- 
matter, which forms a white 
compound. The sulphurous oxide may be driven out of 
the compound by a stronger acid or an alkali, leaving the 
original pigment. If a red rose is held over burning sul- 
phur it is whitened, but the color is at once restored by 
dilute sulphuric acid. If woolens, after sulphur-bleach- 
ing, are washed with a strong alkaline soap, the acid is 
neutralized by the alkali, the coloring-matter liberated, 
and the yellowish tinge restored. The bleaching-power of 
sulphurous oxide may be illustrated by burning sulphur 
under a glass, within which are some highly colored flow- 
ers (Fig. 100). 

301. Sulphurous Acid, H 2 S0 3 . — The solution of sul- 
phurous oxide in water is believed to contain a compound 
having the formula H 2 S0 3 , which possesses strong acid 




Fig. 100.- 



-Bleaching by Sulphurous 
Oxide. 



SULPHURIC ACID. 



L75 



properties. It is sometimes used tor the nine purp 
for which sulphurous oxide is employed. The hydrogen 
in this oompound is replaceable wholly or in part by me- 
tallic elements, giving rise to two classes of -alt- known as 

; ami normal sulphites. 

302. Sulphuric Oxide, &O t (Sulphur Truwide).— This 
may be obtained in the form of a white, showy solid, by 
heating "fuming" sulphuric acid, ami collecting the 
tunes which are given <>tr in a receiver surrounded bj a 

freeiing mixture. It melts at lfi ('. While in this Bolid 

state it may be handled with impunity, if the hands are 

dry; but it fumes in the air, and rapidly absorbs moisture. 
L6D thrown into water it hisses like a hot iron, eombin- 
eagerly with the water to form sulphuric acid. 

303. Sulphuric Acid, R&0 4 (Oilof Vitriol).— This im- 
portant chemical compound was mentioned as early as the 
fifteenth century, and was probably known in the eighth. 
It is found in a free state in the u vinegar-springs " oi 
folcanic regions, and in the saliva of certain animals. Sul- 
phuric arid may be prepared on a small scale in an ap- 
paratus represented by Pig. 101. A large glass balloon, a, 




: PrepAn 



with t: pplies 

mlphuro itfa uitrogeu di< 

with steam, and the ihorl tube furnishes air. Then four 



176 DESCRIPTIVE CHEMISTRY. 

substances react upon each other with the continued pro- 
duction of sulphuric acid. In order to convert sulphur- 
ous oxide (S0 2 ) to sulphuric acid (H 2 S0 4 ), it must have 
oxygen (0) and water (H 2 0) added to it. The steam 
yields the water and the nitrogen dioxide yields the oxy- 
gen, the part which the air plays being to replenish the 
nitrogen compound with oxygen, so that it may continue 
its work. If the sulphurous oxide could take its oxygen 
directly from the air, the nitrogen dioxide would not be 
needed ; but it can take up only nascent oxygen, and this 
is set free from the nitrogen dioxide, which becomes re- 
duced to the monoxide (NO). The process may be repre- 
sented by the following reactions : 

a. N0 2 + S0 2 + H 2 = H 2 S0 4 + NO. 

b. NO + = N0 2 . 

The oxidation is begun by vapor of nitric acid, which 
thereby loses H 2 as well as 0, being converted to NO. 
Also, besides N0 2 , a quantity of N 2 3 is formed, and takes 
part in the work of oxidation. 

304. Manufacture of Sulphuric Acid. — In the manu- 
factory the balloon of Fig. 101 is represented by large 
chambers lined with sheet-lead, on which sulphuric acid 
has less action than on other common metals, and the 
flasks by furnaces (Fig. 102). In one furnace crude native 
sulphur, or the sulphur in pyrites, is burned, and pours 
into the chamber sulphurous oxide (S0 2 ). In another, 
niter is heated in an iron pot with sulphuric acid, by 
which fumes of nitric acid (HN0 3 ) are produced and de- 
livered into the chamber. Steam and air are thrown in 
by another flue, and thus the conditions of action are se- 
cured. The mixed gases are drawn through a series of cham- 
bers by the draught of a tall chimney connected with the 
last one. The bottom of the chambers is always kept cov- 
ered with water to the depth of two or three inches, to ab- 
sorb the acid as it falls, and partitions with openings at the 






SULPHURIC ICID. 



177 



- t<> coin.' in contaH with the surface 
of tli og from kiamber to the i 

When the liquid has 

aired a density of 
l # 8 by the absorption 

acid, it is dmw n oil 
ami boiled down in lead 

pans and glaSBOr plati- 
num retorts, until it 
has a specific grarityof 
i\ L»a The add 

thus obtained has the 
formula H><> 4 , ami 
ordina- 
ry sulphuric acid of 

wing up the 
d from the air sup- 
plied to the chain' 
a constantly increasing 

ount of nitroj 
mains in the atmos- 

>f the chamb 
and would stop the op- 
if it were not 

1 through the 

chin:' Theoreti- 

cally, a small quantity 
■cid ironld 

unlim ; - 

mtlty of sulphur 

ilpliuric arid : 

bat a certain amount 

of oxides of nitrogen 

»<t in tl 
which escapes from 




M 



I 

I 






178 DESCRIPTIVE CHEMISTRY. 

the chimney, so the niter and sulphuric acid in the fur- 
nace must be replenished occasionally. Before reaching 
the chimney the mixed gases are passed through two tow- 
ers filled. with coke, that in the first tower being kept wet 
with concentrated sulphuric acid, which absorbs most of 
the oxides of nitrogen, and prevents their loss. The coke 
in the second tower is kept wet with water, which, after 
the gas has passed through it, is used on the floor of the 
chamberSc 

305. Properties. — Sulphuric acid is a thick, oily liquid 
of 1*85 specific gravity, without odor, and has at first a 
soapy feel, but it speedily corrodes the skin, causing an 
intense burning sensation. It is a corrosive poison. It 
is the most powerful of acids, and has a very strong 
affinity for water. A splinter of wood dipped into it 
for a short time, turns black, the acid taking away from 
it the elements of water, and leaving the carbon. In 
like manner, it decomposes and chars the skin and most 
other organic substances. If a little concentrated acid 
is exposed to the open air in a shallow dish it will soon 
double its weight from the moisture absorbed. When 
sulphuric acid and water are mixed, they shrink in bulk, 
and heat is produced. A mixture of four parts con- 
centrated acid to one part water (Fig. 103) evolves suffi- 
cient heat to boil ether in a test-tube. When 
cooled to —3.0° C, an acid containing 98*5 
per cent of pure acid forms crystals of 
H 2 S0 4 . Such an acid when heated boils at 
338° C. Pure sulphuric acid is colorless, 
fig. 103.— Boil- but slight traces of organic matter, as dust 
mg Et er. ^ gtrawg ^ tum ^ of the dark shade usually 

seen in commerce. The commercial acid is cheap, but 
impure, containing traces of lead, arsenic, potash, hydro- 
chloric acid, and sulphurous oxide. The test for sul- 
phuric acid is a solution of barium chloride, a precipitate 
of white barium sulphate forming if there is any sul- 




romm sulphuric acid, 179 

phuricacid in the liquid to which the chloride is added 

Tii. I when oold acts feebly on the metals, but, 

en boiled, with mod oJ them its hydrogen is displaced 

by the metal, forming a sulphate. Dilate sulphuric acid 

me metals, tor example i 

Zn + ll.s<> 4 = ZnS0 4 + II, 

Sulphuric acid, being dibasic, forma acid as well as nor- 
mal sulphates. 

306. Uses. — Sulphuric acid is one of the most impor- 
• substances used in manufactures. It is employed to 

make sodium carbonate, citric, tartaric, acetic, and nil 

Is, sodium and magnesium sulphate, and various pail 

also, in dyeing, calico-printing, gold and silver refini 

I in purifying oil and tallow. Its chemical uc 
innu; 

Uphurii known 

manufactured hy the original |»n 

distillation of dried ferrous sulphate in earthen re- 
ts. It is a heaw, oily liquid of 1*9 specific gravity, 
fuming strongly in contact with the air. Seal decom- 
poses it into sulphuric and sulphuric oxide, 'i 

I by which this acid is obtained from ferrous sul- 
pl. • green \ itriol," _ 1 to the name M oil of 

vitriol," by which Bulphuric acid is -till frequently 
in 

307. Thio- orSulpho-Compounds.- < )u in- am- 
biance I nlphur 1 that element in ms 
compounds. 7 

phur), also call* 

ilphuric acid by hai 
n of sulphur 
e acid has 1 obtained, but 

salts ar The most in 

• •f soda. I 



180 DESCRIPTIVE CHEMISTRY. 

acid, also in photography and metallurgy for converting 
the insoluble haloid salts of silver into a double thiosul- 
phate (NaAgS 2 3 ), which is soluble. 

§ 3. Selenium. 
Symbol, Se. Atomic Weight, 19 ; Quantivalence, II, IV, VI. 

308. Selenium is a rare substance, existing in several 
modifications, apparently corresponding to those of sul- 
phur. Its name was taken from a Greek word, meaning 
the moon, because it is a companion to tellurium, as the 
moon is to the earth. It was discovered in 1817, by 
Berzelius, in the refuse of a sulphuric-acid factory. It 
is found native, but more frequently in combination with 
metals, as selenides, and it occurs as an impurity in native 
sulphur. At ordinary temperatures it is a solid of a brown- 
ish-red color, and with a luster somewhat resembling that 
of the metals. Selenium boils at 700° C. Heated in the 
air it burns, emitting an intolerable odor resembling de- 
cayed horseradish. The crystalline form, prepared from 
the red amorphous form by heating, has a bluish-gray 
color. It is a conductor of electricity. Its electrical re- 
sistance is diminished by exposure to light, but is restored 
when the light is withdrawn. On this property depends 
the construction of the photophone, an instrument for 
transmitting sound, which differs from the telephone in 
using a beam of light instead of the conducting wire. 
Selenium forms oxides, acids, and chlorides similar to those 
of sulphur; it also forms seleniureted hydrogen, a very 
ill-smelling and irritating gas. Selenium is soluble in 
sulphuric acid, but is thrown down when the acid is di- 
luted with water. 

§ 4. Tellurium. 

Symbol, Te. Atomic Weight, 128; Quantivalence, II, IV, VI. 

309. Tellurium was first distinguished in 1798, by 
Klaproth, who named it from the Latin, " tellus," the earth. 



LRBOK [g| 

It is found in nature, both tree ind in the form oi 
keUurides of metals, hut is exoeedingl j rare. It ifl ■ Un- 
ite, brittle, metal-like substance, crystallising in rhom- 
bohedrons, melting at about r><' I .. and volatilising at 
a white heat Seated in the air it takes fire, and barns 
with ■ lively (doe flame, edged with green. The vapor of 
tellurium has a greenish-yellow oolor Tellurium is sol- 
uble in sulphuric acid. In its compounds it resembles 
liuni and sulphur. 



OHAPTEB XVI. 

I DRIYAJLBKl BTOH-H SI LL8. Oi &BON, 31 LI< 

gl. Ca 'ban. 

\-2 ; Quantiv.il.'iKv, II ind IV 

■ ity mt Diana nd i. 

310. History and Occurrence.— I larbon, fro in the Latin 
carbo % eharooal, is the name applied to the solid with which 

miliar in the various forms of charcoal, mineral 
coal, soot, black-lead, etc. It is met with in three well- 
marked allot rop: the diamond, graphite, and 

phous carbon. It oooun in nature in the b 
as dia graphite, and mineral coal, and mora abun- 

dantly in combination si oarbon dioxide in the air nd 
rs; as cs . farming 

large HK-k-ru "nibiued with hydrogen in bitu- 

men, petroleum, and natural gas. It Conns about half 
the solid matter of all vegets 
par* mimal ti 

311. The Diamond. \ 1 id s appear more unlike 
than dull. Mack, soft charcoal, and the brilliant, trans- 

nt, bard diamon 
stance The purest form of >nd, I: 



182 



DESCRIPTIVE CHEMISTRY. 



crystallizes in regular octahedrons or other forms of the 
monometric system, the facets being frequently convex 
(Figs. 104, 105, 106), and is the hardest body known. 






Fig. 104. 



Fig. 105. 



Fig. 106. 



Diamonds are found in the earth in various places, usually 
in the form of rounded pebbles covered with a brownish 
crust. A few have been found in the Southern and the 
Pacific States ; the most important diamond-fields are in 
India, Brazil, and South Africa. Of their mode of pro- 
duction nothing positive is known. The finest specimens 
are perfectly colorless, but others are yellow, green, blue, 
or black. The diamond is the hardest substance known, 
whence its old name, adamant. It has never been melted, 
and successfully resists the action of all chemicals. It 
burns in air or oxygen without great difficulty, the prod- 
uct being carbon dioxide, which is proof that the dia- 
mond is carbon. It is a non-conductor of electricity, but 
in the flame of the electric arc it becomes white - hot, 
swells, and is converted into a black, coke-like mass, 
which conducts electricity readily. The diamond has a 
very high refracting power, by which it flashes light of the 
most varied and vivid colors. This property gives it the 
beautiful brilliancy which makes it the most highly prized 
of gems. The facets of a diamond, as seen in jewelry, are 
not the natural faces of the crystal, but are produced by 
"cutting" or grinding the stone so that its refracting 
power will show to best advantage. The other uses of 
the diamond depend upon its hardness ; thus, it is used 
for cutting and writing on glass, and for drilling rock. 







BftAPfil Is;; 

nd-dusl is used in cutting and polishing diamoa 

I other gems. Only the natural curved e< 

3 will cut The dark-colored and otherwise 

lees valuable diamonds are used for those latter purpo>e>. 
312. Graphite, or Plumbago, is another allotropic form 
of carbon. It La found in rocks, sometimes in considerahle 
masses, and crystallises in six-sided plai 
of a grayish-black color and metallic luster, 
resembling lead (Fig. 107); henoe H 
b-lead. Its specific gravitj 
about 2. It resists the action of intense 
heat, and is useful to the chemist in mak- 
_ crucibles. It is friahle, leaving a hlack 
ma d rubbed, has a greasy feel, and 

ised instead of oil to lessen the friction 
of machinery. It is unaffected by air and moisture, and 
hence forms a valuable coating to protect iron-work from 
rust; and, as it resists heat, it is fitted for stove-polish, 
[ten adulterated with lamp-black, which may be 
I by heating the suspected .-ample t<> redness, when 
tlie lamp-black burns away. The mosl important oa 
iphite is in the manufacture of pencils. For thifi pur- 

pos- red, mixed with washed clay, and the pla$- 

18 is then forced through an iron cylinder having a 

small hole in the end, from which it Comet 0U< in the form 

a wire. [| u then cut into the proper length, and 
>ved cedar sticks, when the pencil is com- 

B I graphite IS apparently 

llling a kni : ning a 

lead-jM-neil, more than cutting wk ■ much harder 

substances. It is a good conductor of electricity, hence it 

mold- on which I 
mac 

When cast-iron, which hafl been melt on- 

tallisei out i: 



184 



DESCRIPTIVE CHEMISTRY. 



313. Amorphous Carbon. — The third well-settled allo- 
tropic variety of carbon is obtained when any organic 
substance, as wood, bones, or sugar, is strongly heated or 
burned with a partial exclusion of air. Several common 
substances are included under this name. 

Charcoal is ordinarily prepared by covering large heaps 
of wood with ashes or turf (Fig. 108), and burning them 




Fig. 108.— A Charcoal-Heap. 

with a limited supply of air, so as to prevent complete com- 
bustion, and only char the wood. The finer kinds of char- 
coal, such as are used for making gunpowder, are produced 
by distilling the wood in close iron retorts. Tar, wood- 
spirit, and acetic acid, are also products of this operation. 
Charcoal is a black, brittle, inodorous, tasteless solid; a 
good conductor of electricity, but a bad conductor of heat, 
and perfectly insoluble in all liquids. It is oxidized by 
strong sulphuric acid : 

2H 2 S0 4 + C = 2H 2 + C0 2 + 2S0 2 . 

It resists the action of air and moisture, and is, therefore, 
very unchangeable. Timbers, and grains of wheat and 
rye, converted into charcoal eighteen hundred years ago, 
at Herculaneum, remain as entire as if they had been 
charred but yesterday. Wooden posts are rendered more 



fHAROOAL, [gg 

double by charring their ends before placing them in the 

ground. 

The chief use of charcoal is as a fuel. When pure, it 
hums without flame, although it usually contains watrr 

which, daring the combustion, n partly deoompoeed and 
rbon hydride is formed, which hums with a slight flame. 

ttbic fool of charcoal from soft wood weighs from 8 t<> 
".♦ lbs.; from hard wood, from 1$ to i:> 11». ; hence, hard- 
wood coal is best adapted to produce a hiirh heat in a small 
space. At high temperatures, charcoal has a very power- 
ful affinity for oxygen; therefore it Lb of great value in 

the smeltinLr-furnaee in reducing metallic oxides, the form 
• from which many metals are obtained. 
314. Absorptive Power of Charcoal. — Saying the 

Structure of the wood from which it was derived, char- 
coal is very porous, and it possesses in a remarkable 

degree the power of abeorbii b, and condensing 

them within its It will absorb Ho times its bulk 

iinnionia, 35 timet its bulk of carbon dioxide, and '.♦ 

times its bulk of oxygen. Freshly burned charcoal ini- 

bibei watery vapor from the air very gree dily, and by a 

wee ses in weight from 1<> to 80 per cent. 

Th< »al havinsr the finest pores possesses this power 

of absorption in the greatest degree; the spongy SOri least 
M A Cubic inch of charcoal," .-ays Liebig, "must ha\.. 

least computation, a surface of LOOsquan It 

abs and ill-smelling L f :ises ; fonl watrr tiltei 

through crushed charcoal, and tainted neat packed ii 

.' :■-••■:•■ . • _. h also has tie- power of with- 

dru oloring-matteri and other substances from 

liquids. The charcoal from bones (bone-black) i- roperior 

towood d for purifying purj • Iv 

uaed ii. n to d« 

wines, etc., I in the sane- wa\ 1 

in water-filten and in n .rs. 

315 Its Deodorant Action, (hi: rful 



186 DESCRIPTIVE CHEMISTRY. 

deodorizer and disinfectant, but it is not an antiseptic, or 
preventer of change, as has been supposed. In fact, it 
is an accelerator of decomposition. It was formerly 
thought that charcoal acted by simply sponging up the 
deleterious gases, and retaining them in its pores; but 
it has been lately shown that, by means of its condens- 
ing power, it is a powerful agent of destructive change. 
The condensed oxygen seizes upon the other gases pres- 
ent, and, oxidizing them, forms new products. It thus 
changes ammonia to nitric acid, and sulphureted hydro- 
gen to sulphuric acid. The body of a dead animal 
packed in charcoal emits no odor, but, instead of being 
preserved, its decomposition is much hastened. This 
property has been made medically available in the form of 
charcoal-poultice, to aid in the removal of sloughing and 
gangrenous flesh in malignant wounds and sores. Freshly 
burned charcoal sometimes takes fire spontaneously, from 
the great heat produced by the condensation of oxygen. 
Lamp-Mack is an impure variety of charcoal. It is the 
soot deposited from the burning of pitchy and tarry com- 
bustibles. The smoke is conducted through long horizon- 
tal flues terminating in chambers hung with sacking, upon 
which the lamp-black is deposited. It is used for making 
printers' ink, shoe-blacking, and black paint. 

316. Mineral Coal consists of carbon, mixed with more 
or less of compounds of carbon with hydrogen and oxy- 
gen, and some mineral impurities which form the ashes. 
Like charcoal, it is a product of the heating of wood 
out of contact with air. Our supply of coal was formed 
ages ago, the action of water and great pressure taking 
part in the operation. An immense quantity of carbon 
dioxide in the air at an early period in the earth's history 
supplied food for vast forests of gigantic plants, which 
were afterward thrown down and covered with mud and 
sand. The internal heat of the earth, then much greater 
than now, caused the change of these great beds of woody 



mi\i:i; \i. OOAL |gf 

materia] into ooaL The change i in driving out 

the hyd aid oxygen of the wood, combined with i 

little of the carbon, and it is tnoel peri eotly done in the 

-beds. The variety oi ooal thus formed is oalled 

anthracite, and about '.mi percent of it is oarbon. 1 
hard, brittle, shiny, and burns with alni(»t no flame. The 

• anthracite fields in the world arc in 1 N'li n>\ 1 \ an i;u 

oal in common use for house-fires in the 
: United S i. Bituminous ooal is leaa perfectly 

carbonized. I; ter and len shiny than anthracite, 

vith much flame, a portion of the oarbon gen- 
tly escaping unburned as smoke. From 75 to 80 per 
bituminous coal is carbon. Large deposits of it 
ir in tie Western United States and in the British 
it is in genera] nc vm I or candle coal 

(so called because a small fragment burns with a bright 
flame, like a candle) is a variety of bituminous COaL It 
has a dull surface and breaks into cubical blocks, tl 

;d for open-grate Area Jet resembles can- 

nel c<»ab but is harder and more lustrous, which make- it 

In or brown eoah the 

I from wood has been still less complete. It oon- 
-s than j» prr cent of carbon and o?er 80 

h to the process by which odd ifl formed is 
agon at the present time in swamps which are n 

ad blades of grass are changed 
to a substance called prat, which is used as fuel in [rels 

en coal is heated in r< 

•-.which form common lighting gas and ooal-1 
v The coal left behind bai 
called coke. It burns without nnok 

. which do.-s not hi>t long. 1 ised 

mostly in extractii • : in- 

dustrial purposes, and !• ■-- cnnnnoiilj in the household 



188 DESCRIPTIVE CHEMISTRY. 

A part of the gaseous compounds of carbon formed in 
the distillation of coal are decomposed by contact with the 
hot retort, on the sides of which the carbon in them is 
deposited. This gas-carbon resembles graphite, and is a 
good conductor of electricity. It is used for one of the 
plates in Bunsen's, Leclanche's, and other batteries, and 
for the points (" carbons ") of the arc electric light. 

317. Carbon Monoxide, CO (Carbonic Oxide), is a 
colorless, almost inodorous gas, of nearly the same weight 
as air, which burns with a pale-blue flame. It is produced 
by burning carbon with an imperfect supply of air, and 
its formation may be observed in an open coal-fire. At 
the lower part of the grate, where the air is abundant, car- 
bon dioxide is formed. As it ascends into the hot mass 
above, it loses half of its oxygen, becoming carbon monox- 
ide. The liberated oxygen, combining with the carbon of 
the fuel, also produces an equal quantity of the gas. As 
the carbon monoxide thus formed rises to the surface of 
the fire, it burns to carbon dioxide, with a lambent, blue 
flame. Its escape unburned means a waste of fuel. This 
gas can be liquefied and solidified by cold at ordinary 
pressure, but has not been liquefied by pressure without 
cold. Carbon monoxide, when respired, acts as a violent 
poison. Even when mixed with a very large quantity of 
air it produces giddiness and headache, and has in many 
instances proved fatal. Common coal-gas contains from 
4 to 7 per cent of carbon monoxide, and the kind called 
" water-gas " may contain over 30 per cent of it. 

318. Carbon Dioxide, C0 2 (Carbonic-Acid Gas, Car- 
bonic Anhydride). — This compound was discovered by 
Van Helmont about the beginning of the seventeenth cent- 
ury. There is always a small quantity of it, about -04 
per cent, in the air. Wherever carbon in any of its modi- 
fications, or any compound of carbon, burns with free ac- 
cess of air, carbon dioxide is produced. The burning of a 
bushel of charcoal forms 2,500 gallons of the gas. It is 



CARBON moxirn-:. 



\s\) 



produeed by fermentation, by the don deco mp osition 
gaiiic bodies, and also by the respiration of animala 

h adult man exhales about U<> gallons per day. Two 

oandles produce as much of this gas as a peitoon in the 
same time. It : reduced by chemical changes which 

take place in the interior of the earth, and it oomea np 
with ti. hich rise to the buj In foloai 

lonallv met with, unmixed with other 

gases, llisimr to the surface, often more rapidly than it 
diffused into the air, invisible pools and ponda of it 
imulate in hollows of the ground. Through the a 

bra* He del ( in Italy, a man may walk un- 

harmed, though he wade knee-deep in carbon dioxide, but 
a dog with its nostrils near the earth is sulloeated on en- 
tering. The poifi 
valley of JaVS : 

of carbon diox- 

Blled with the 
bleached bones of 
dead animal 

319. Prepara- 
tion. — Carbon 

'.v obtained by 
icid 

d small frag- 
ments of marble, 
eha 

• of lin 
Any strong acid will 
answer the purpose, but hydrochlork acid i- the best 
laced in a flask I with water. 

A little dilufc a poured down through the fun- 

nel fa 




i*k for gcDcratn 






190 



DESCRIPTIVE ' CHEMISTRY. 



and the gas escapes through the bent tube. It may be 
collected over water in the pneumatic trough, or, as it is 
heavier than the air, it will quickly displace the latter in 
an open vessel. The change is thus shown : 

CaC0 3 + 2H01 = CaCl 2 + H 2 + C0 2 . 

A cubic inch of marble will yield several gallons of the 




Fig. 110.— Pouring Carbonic 
Acid. 



320. Properties. — Carbon dioxide, at ordinary tem- 
peratures and pressures, is a colorless, inodorous gas, of 
1*53 specific gravity. It does not sup- 
port combustion. To prove this, we 
have but to place a lighted taper in 
a beaker, and pour carbon dioxide 
upon it from another vessel (Fig. 
110) ; the invisible current prompt- 
ly puts out the light. That this 
gas is much heavier than air may be 
shown by weighing it in air (Fig. 

ni). 

When respired, carbon dioxide is 
fatal to life. If pure, it produces spasm of the glottis, 
closes the air-passages, and thus kills suddenly by suffoca- 
tion ; but, though it has been held that this gas exerts a 
poisonous action, it is more probable that these effects are 
merely due to deprivation of oxygen. It has no poisonous 
effect when taken into the stomach. This gas often ac- 
cumulates at the bottom of wells, and in cellars and coal- 
mines, where it is called " choke-damp," stifling those who 
may unwarily descend. To test its presence in such cases, 
it is common to lower a lighted candle into the suspected 
place, and, if it is not extinguished, the air may be 
breathed safely for a short time. If the light goes out, it 
will be necessary before descending to let down dry-slaked 
lime to absorb the gas. When carbon dioxide is brought 
in contact with calcium hydrate solution (lime-water), the 



CARBON IHOXIPK. 



191 



liquid turns milky, from the production of calcium car 

lime-water to tin- air, 







in ■ short time its surfs lovered with a thin film <>f 

inm car proving that there is carbon dioxide in 

If we blow through a tube into a irlass 

it quickly beoomee turbid from the nine 

cause, thus showing that there is oarbon dioxide in the i 

. Und tmoepb i 

carbon dioxide shrinks into a colorleaa, limpid liquid liL r ht- 

than water. WTien this moved, it d< 

I nil 
such rapidity t: 

I freexes it to a white solid, like dry mow. This solid 
carbon wastes away but slowly, and may 

tough, if left lorn: upon the -kin, it has tin- sai 
effect as a red.) 

321. Uses. parklingap] L lively, ] 

gent taste of various mineral in ion 

Water abec 



192 DESCRIPTIVE CHEMISTRY. 

ume of this gas, but by means of a forcing-pump it may 
be made to receive a much larger proportion. "Soda- 
water " is only water charged with carbon dioxide. Being 
overcharged, when the pressure is withdrawn, the gas es- 
capes with violent effervescence. The effect is the same 
whether the carbon dioxide is forced into the water from 
without, or generated in a tight vessel, as is the case with 
beer and champagne; the gas gradually formed is dis- 
solved by the water, and, escaping when the cork is with- 
drawn, produces the foaming and briskness of the liquor. 
In watery solution, carbon dioxide is supposed to exist 
in combination with water as C0 2 4- H 2 = H 2 C0 3 , or 
carbonic acid. By replacing the hydrogen by 2 atoms of 
a univalent or by one atom of a bivalent element, carbon- 
ates are produced : 

Na 2 C0 3 Sodium carbonate. 
CaC0 3 Calcium carbonate. 

They are easily recognized by the effervescence ensuing 
when they are brought in contact with an acid. 

Carbon dioxide is also used to extinguish fires. In one 
case an English coal-mine, which had been on fire thirty 
years, was completely extinguished by pouring into it eight 
million cubic feet of this gas. In the " fire-annihilators " 
or " extinguishers," which consist of a large metal jar, to 
which a hose is attached, this gas is used, but not to 
smother the flames. It serves merely by its pressure to 
force a stream of water from the apparatus. 

322, Carbon Bisulphide, CS 2 {Bisulphide of Carbon). 
— This is a colorless, very volatile liquid, heavier than 
water, which boils at 46° C. When pure it has an ether- 
like smell and a pungent taste, but impurities give it a 
yellowish color and a very disagreeable odor. It does not 
solidify at —110° C, but, by blowing a strong current of 
dry air over its surface, part of it is converted to a snowy 
solid. It is volatile at ordinary temperatures, and burns 



OYANOG 

I . yielding carbon dioxide and sulphur diozi 
U sulphur, phosphorus, iodine, oils, u r unis, resins, 

• l i> dissolved in alcohol and ether, bu1 noi in 

roduoed by bringing vapor of sulphur into 

atact with red-hoi charcoal, the disulphide vapor being 

sed in eold vessels. From its liLdi ilis]u»rsivt» power 

r light, it is used to till hollow prisms of i^lass for 

gpc< 'cat oold does not solidify it, it is Of 

in thermometers instead of mercury for indicating low 

• res; its solvent power makes it useful in the 
manufacture of rubber goods, for removing oil from wool, 
and other industrial operations; and, as it is poisonous, it 

1 for killing vermin, especially insect- in grain* 
Carbon fori nil chlorides and bromides, but no 

compound with iodine is known. It unites at high tem- 
ratures with some metals, such as iron, manganese, and 
iridium, forming <<trf>if/rs. 

323. Cyanogen, OgN* — This substance may be 
procured by heating mercuric cyanide, Sg (( V>, in a 
glass tube or retort. The compound is decomposed, cyano- 

being evolved as gas, which may be 

burning with a beautiful purple 

flan- L12). Cyanogen is a transpar- 

ss gas, poisonous it" respired, and 

wit!. I v soluble in 

water, and hen Uected over 

urv. It is condensed to a color 
limpid liquid by pressure, or a cold of — 

a transparent crystalline 
solid at a still 1 mperatu* . I mo- 

thougfa not an element, 

lis forming com- 
lar to I 
It is 1 urded as a compound i 

symKol : 

324. Hydrocyanic Acid. Eft \ i /' 




194 DESCRIPTIVE CHEMISTRY. 

substance is best obtained by the decomposition of various 
metallic cyanides with a strong acid, and subjecting the 
mixture to distillation. When pure, it is at common 
temperatures a colorless liquid, which solidifies at — 15° C, 
and boils at 27° C. It has the peculiar odor of bitter 
almonds or peach-blossoms. It is exceedingly poisonous, 
one drop producing instant insensibility and almost in- 
stant death. The inhalation of the vapor should, there- 
fore, be most carefully guarded against. The prussic acid 
of the shops is a more or less dilute solution of hydrocyanic 
acid in water. Kernels of bitter almonds, cherries, and 
prunes, and the leaves and bark of several species of 
Prunus, contain amygdaline and emulsine, which, in 
contact with water by fermentation, are converted into 
oil of bitter almonds, hydrocyanic acid, and sugar. 

§ 2. Combustion. 

325. Combustion a Chemical Process. — Combustion, in 
its popular sense, is that familiar process which is ac- 
companied by heat and light, and which most commonly 
takes place between the oxygen of the air and substances 
containing carbon, such as wood, coal, and oil. The 
chemist, however, gives to the term a wider meaning, 
which includes all those forms of chemical action that 
result in the combination of substances with one or more 
surrounding gases ; thus, the violent burning of iron in 
oxygen or its slow rusting in the air, the rapid consump- 
tion of wood in the furnace, or its gradual decay, are to 
him all cases of combustion. The nature of the gaseous 
atmosphere also makes no difference, and the burning of 
phosphorus or arsenic in chlorine gas, of hydrogen or iron 
filings in sulphur - vapor, are instances of this form of 
chemical action, as well as the corresponding changes 
taking place in air, or oxygen gas. Bodies were formerly 
divided into combustibles and supporters of combustion. 
Oxygen was held to be the universal supporter of com- 






I DMBUSTIOfl [95 

ition, while hydrogen, carbon, and iron, irhiefa burn 

it, were called combustibles. Hut oxygen will born just 
as well in hydrogen, which thus becomes the supporter 
oombostion; and the fact is, the action is mutual and of 

the same kind oil the part of both. 

326. Rapid Combustion.— Combustion which L r "< - on 
Idly, and with the production of much light and heat, 

illed rapid combustion. In order that bodien may 
combine in this way, they must be tirst raised to a oertain 

temperature, called their point of ignition, and the nun- 

bastion will L r <> on only bo Long as the bodies are kepi at 

this temperature. After a substance is once kindled, 

however, the heat given off by the rigorous chemical ao- 
. is usually more than enough to keep up the oombus- 
d until one of the combining bodies is consumed* The 

perature at which rapid combustion may take place 

differs with different bodies. Thus, in atmospheric air, 
phosphorus ignites or kindles a( r» c, sulphur at LIS I ., 
while the hydrocarbons require ■ temperature of about 

I to kindle them. The stability of the order of 

nature depends upon the gradation of the affinities be- 
itmospheric oxygen and the hydrogen and carbon 
of organic bodies. These arc only brought into aetioi 

emperatures. Did these bodies, like phosphoruSi 
it a much lower degree, conflagrations, which i 
now comparatively rare, would become oniyersaL 

extremely rapid combustion* Bxplo- 
8ive combustion of gaseous bodies depends on sudden i 
pansion of the compound by the liberated heat, which, 
immediately followed by contraction, the 
to till the vacuum caused by the cooling of I 

:id. 

327. Slow Combustion — Oxygen, ai weD 

•its, frequently enters in1 ombinationaJ ordini 

ttures and without p 

ing of iron in 



196 DESCRIPTIVE CHEMISTRY. 

and animal substances is the slow action of oxygen. The 
complete burning of a combustible body requires the con- 
sumption of the same quantity of oxygen, whether the 
process goes on rapidly or slowly, and the amount of heat 
set free is the same ; but in the former case it requires 
years for its development, and in the latter only as many 
minutes. Therefore, the intensity of the heat depends 
upon the rapidity of the combustion. Heat would be 
liberated from the burning of a pound of coal in ten 
minutes, six times as fast as if its combustion occupied an 
hour. 

328. Spontaneous Combustion. — Sometimes, under fa- 
vorable circumstances, the combination becomes so rapid 
that the accumulated heat produces ignition, causing the 
phenomenon called spontaneous combustion, or more prop- 
erly spontaneous ignition. This is most liable to occur 
with porous or fibrous substances, which expose a large sur- 
face to the air. Woolen or cotton rags saturated with an oil 
capable of absorbing oxygen rapidly and then laid away 
in heaps, often ignite in this manner, especially if exposed 
to the sun. 

When spontaneous combustion is mentioned in old 
books, it refers to the baseless notion, once widely believed, 
that the living human body, in favorable circumstances, 
would take fire and burn up. As alcohol burns very easily, 
the mysterious disappearance of persons who were known 
to indulge freely in alcoholic drink was accounted for in 
this way. 

329. Cause of the Heat. — It has been explained that 
chemical action produces heat by conversion of the motion 
of chemical atoms into heat- vibrations. We have atoms 
separated and powerfully attracted, like lifted weights; 
they rush together, collision arrests motion, and their force 
is given out as heat. It is the clash or impact of the 
atoms of oxygen against the elements of burning bodies 
which gives us the heat and light of combustion. By fig- 



VUTKK of PLAMB, [97 

Bring to ourselves the atom- shot the moleeutor 

spares with irrcat foree, and thus parting with their mo- 
tion, we have an explanation of the source of heal in com- 
bustion which is in harmony with our latest knowledge 

the nature of heat, and of its other modes of produc- 
tion, while in no other way is it possible to explain its 

mical origin. 

330. Nature of Flame. — Flann * heated 
to incandescence. Substanoes which hum with flame an 

gases already, or they contain a gafl which is set fire 

the heat of combustion. Different gases give off differ* 

amounts of light In the burning of pure oxygen and 

hyd the flame gives oil intense heat, but bo little 

.t thai it can hardly he Seen. The presence of a solid 

which can be heated to incandescence in ■ flame in* 
ises the illumination. If into this non-luminous flame 

rift a little charcoal-dust, the particles of Bolid carbon 

antly heated to ineandesoenoe, and there is a bright 
flash of light 

331. The Compound Blow-pipe. The conditions of 
illumination are fulfilled most perfectly in the, compound 
blow-pipe. The two erases are supplied from gasoi 

India-ruhher hair- ( Ki.ir. 1 !•>)< which are conneeted by 

able tuhes with the (Big. L 14) ; the flow being 





pressure on the bags, and controlled 

erases are emitted together and il the 

Whi e rise to 



198 DESCRIPTIVE CHEMISTRY. 

which is hardly visible, but which has intense heating 
power. A steel watch-spring burns in it with a shower of 
scintillations. Substances which do not fuse in the hot- 
test blast-furnaces melt in this heat like wax, or dissipate 
in vapor. 

332. The Lime-Ball. — A little ball of lime, however, of 
the size of a pea, remains unaltered in the flame. It glows 
with a blinding brilliancy, producing what is known as the 
" Drummond light," or the " calcium light." It is em- 
ployed as a substitute for the rays of the sun in the solar, 
or oxyhydrogen microscope, and is used in coast-surveys 
for night-signals, and in the stereopticon. In all ordinary 
illuminations the principle is the same as that of the lime- 
light. The substances employed are compounds of carbon 
and hydrogen ; the union of oxygen and hydrogen gives 
rise to heat, and the luminous carbon particles at the same 
time set free in the heated space are the source of the 
light. The amount of light produced by a glowing solid 
substance depends on its temperature; many times as 
much light being given off when it is made white hot 
than when it is heated only to redness. 

333. How the Candle burns. — The materials used for 
illumination, whether solids or liquids, are converted into 

gas before burning. The candle first be- 
comes a lamp, and then a gas-burner. 
When lighted, the heat radiates downward 
and melts the material of the candle, form- 
ing a hollow cup filled with the liquid com- 
bustible (Fig. 115). From this reservoir 
the wick draws up the oil into the flame. 
Here, in the midst of a high heat, and cut 
off from the air, it undergoes another 
change exactly as if it were inclosed and 
heated in a gas-maker's retort; it is con- 
verted into gas, and in this form finally 
FlG 'ingCanme m burned. As the wick rises into the flame, 



ORDER OK TIIK OOMRUSTION. 



L99 




Fig. 11G. The Flame 
hollow. 



it fills the interior with » sooty mass, and interferes wi 
the combustion. 

334. Structure of the Flame. — As the wick remains 
thus unoonsumed in the interior of the flame, it ba obvious 
there can be no tin- there. If we lower 

a piece of <rlass or wire irauze over a can- 
dle or gas flame, as in Kg, 1 18, we shall 
see an interior dark spot surrounded by 
■ ring of tin*. This inner -pace Lb filled 
with dark untamed hydro-carbon va- 
pors, which are in- 
closed by a shell of 
tire, or burning _ 
If one end of a small glasfl tube is 

introduced into the candle-flame, as 
in Kg, IK. these interior gam will 
be conveyed away, and may be lighted 

at the other end. 

335. Order of the Combustion. — 
There is an order <>f combustion in 

n Fi7mr fr ° m tllr H»nWi which depends upon the 

order of affinities. In Pig. 118, a rep- 
the nucleus of hydro-carbon vapor. If oi 

from without had the same affinity for both its elements, 
they would be consumed together, with but little lumi- 
nous effect. But the oxvltcii decomposes the 
gase< pound, and, seizing upon the 

hydroL r m first, surrounds a with the int « 

At the same time the 

earbon-partidei are set i i, being 

'.llite h< out the light 

e the place <>f burning 

d the seat of illumination The 

-cent carbon-particles, ai they pass 

on dioxide in the out. r 




200 



DESCRIPTIVE CHEMISTRY. 




Fig. 119.— Cross-Sec- 
tion of the Flame. 



cone. To prove the constant presence of free carbon in 
the flame, it is only necessary to introduce into it any cold 
body, as a piece of porcelain, when carbon will be copious- 
ly deposited upon it as soot. Fig. 119 
represents a cross-section of the flame 
and the arrangement of its parts; CH 
the unburned carbon and hydrogen, H 
the shell of burning hydrogen across 
which the glowing carbon-particles float, 
and lastly the sphere of burning carbon. 
It will be observed, by noting any com- 
mon flame, that at the base it burns 
blue, and yields but little light. This is because the oxy- 
gen at this point is so abundant that it burns simultane- 
ously both hydrogen and carbon. A candle-flame moved 
swiftly through the air gives a diminished light for the 
same reason. 

336. The Bunsen Burner. — The effect of oxygen on a 
flame is strikingly illustrated in the gas-burner invented 
by the chemist Bun- 
sen (Fig. 120), and 
used for heating pur- 
poses in laboratories 
wherever coal - gas 
can be obtained. 
The gas is delivered 
by a small inner tube 
(seen through the 
holes at d) at the 
bottom of the tube 
e e. Air enters 
through the holes 
and mixes with the 
gas, and the mixt- 
ure, when lighted at 
the top of the burner, burns with an almost invisible but 




Fig. 120.— Bunsen Burner. 



BFFB I "I rSMPERATI RE ON THE I 



201 



CJ 



I II. ( '"I'l" ' 



hot flame. If the holes are dosed, the flame I 

OB its ordinary yellow luminous appearance. The gas 
sometimes takes tire at the inner tube, making a slight 
len the lamp is said to * k map." 

337. Effect of Temperature on the Flame. If by any 
means the temperature ol i flame falls baton a oertain 
point it is immediately extinguished. The flame of a 
candle may be put out by lowering ovw 
it a ooil of cold copper wire (Fig. LSI). 
A piece of fine wire game held across 
the flame of a candle cools the com- 
bustible gases and the carbon-particles below the point <>f 
Ignition, BO that they rise through the meshe.-^hi the form 

of smoke (Pig. LS8), The 

f - ^ ganae may become red-hot 

and still not allow the flame 

to pass, bo rapidly is the 
heal conducted away by the 

wire. Yet the <-<><>l' 

may be rekindled above, 
when the flame will go on 
burning. If the wire gai 
is held 8 or \ cm. above 
the top of a Bunsen bun 
the gas may be turned on 
and lighted above the lt.i 
will burn without the flame passing to the d 

338. Safety-Lamp. On this princi- 

jr-lamp is constructed. The 
f carbon hydride, called by 

the mil ••-damp, in 00al-mi 

cati£«-d immense destruction of life, 

* i t - 
lesdy contrived to i rri- 

ble accident- Sir Humph] 




-t'.j.K the i 




b 



202 



DESCRIPTIVE CHEMISTRY. 



took hold of the subject. He produced a lamp at the 
Eoyal Institution of London in 1816, which was an almost 
perfect means of safety against such explo- 
O sions. The safety-lamp consists simply of an 

ordinary oil-lamp inclosed in a cage of wire 
gauze which permits the light to pass out, but 
prevents all exit of flame (Fig. 124). The 
space within the gauze often becomes filled 
with flame, from the burning of the mixed 
gases which penetrate the network ; but the 
isolation is so complete that the explosive 
mixture without is not fired. Fatal explosions 
still occasionally take place, but they are due 
to carelessness of the miners. As the intensity 
of light depends upon the rapid consumption 
of oxygen, there must be a free supply of air, and 
iafety-Lamp! provision f or the escape of combustion products. 




§ 3. Silicon. 

Symbol, Si. Atomic Weight, 282 ; Quanti valence, IV ; Speicfic Gravity, 

25. 



339. Silicon. — This element is never found free in na- 
ture, but may be prepared by decomposing silicon fluoride 
or chloride with sodium or aluminum. It has three allo- 
tropic states : first, amorphous silicon — a brown powder ; 
second, a crystalline hexagonal variety resembling graphite; 
and, third, a crystalline octahedral form which is exceed- 
ingly hard. It is of little interest except to the scientific 
chemist. 

340. Silicon Dioxide, Si0 2 (Silica). — This compound 
is one of the most important and widely distributed of 
substances. The minerals quartz, chalcedony, jasper, 
and opal, most sandstones, and sand, are nearly pure 
silica. It is also an essential and sometimes the chief in- 
gredient in granite, and many other common rocks. It is 



SILICA. 

found in the Btems iins and grasses; the value of 

tlu k plant called horse-tail (semiring rushes), tor BOOUring, 

Lae to the silica it contains, silica is almost infusible; 

hut by the intense heal of the oxy-hydrogen blow-pipe it 

reduced to a transparent glass, an<l may he spun mit 

into thn ids. It is insoluble in water, and in all acids 

-•pt hydrofluoric, bul it is dissolved by solutions of 

alkaline silicates. Hence, all natural waters which con- 
tain alkaline silicates may also contain s little silica. Also, 
when water containing even small quantit alkaline 

3 upon silica under pressure and at tempei 
tores from 300 c to 400° CL, it is capable of dissolving a 
large quantity of the mineral, which is again deposited 

■n the pressure and heat are removed. This 18 tl: 
of the siliceous deposits formed by certain hot springs, 
like the geysers of Iceland. If wood is present in such 
waters, as it decays, the particles ol silica arc deposited in 
place of those of the wood that escape, and thusaoopy 
of the wood in stone, or a/oinZ, is produced. Ohaloedony 

rk, in Arizona, a thousand acres in extent, Lb 001 1 ired 

h blocks of "agatized wood" formed in this way from 

the fallen trunks of a forest of mighty trees. The itotiy 

si in many cases baa penetrated to the ?ery heart of 
logs over three feel in diameter. 

341. Modifications of Silica. Si li< i two modi- 

fications:* « jrstalline, the other amorphous. 'I 

er is found in nature m 
which probably makes up one third of 

the rocks of the crusl of the globe. U 

crystallizes in the hexagonal system. It 

lite hard, and m. ool- 

ored in fario by impuritii 

crystals are usually 

pyramid- | I 

g of pure Bilira, tin . l V , * rtx 




204: DESCRIPTIVE CHEMISTRY. 

as transparent as the clearest glass. The purest specimens 
are cut and used in jewelry under the name of " white 
stone," and the " pebble " lenses used for the best specta- 
cles and for optical instruments are also cut from quartz 
crystals. Amethyst is quartz colored violet by a trace of 
oxide of manganese. When brilliant and evenly tinted, it 
is highly esteemed as a gem. False topaz is quartz having 
a yellow tinge. Crystals varying from a slight cloudiness 
to almost black are called smoky quartz. In the uncrys- 
tallized form, quartz is also colored red and yellow by 
oxides of iron, and green by iron silicate. 

The amorphous modification of silica is a white solid. 
It occurs in nature as the minerals chalcedony, agate, 
onyx, flint, jasper, and opal, which are variously colored 
by impurities. The opal contains water in combination 
with its silicon dioxide. 

342. Silicic Acid, H 4 Si0 4 (Tetrabasic Acid), H 2 Si0 3 
{Dibasic Acid). — This acid exists in two modifications. 
When silica is fused with sodium carbonate, carbon dioxide 
escapes and a sodium silicate is formed. If this substance 
is dissolved in water and a few drops of hydrochloric acid 
are added to the solution, silicic acid separates as a jelly- 
like mass, which is nearly insoluble in water or acids. 

343. Silicates. — The hydrogen of both forms of silicic 
acid may be replaced by metals, forming ortho-silicates 
from the tetrabasic acid, and meta-silicates from the diba- 
sic acid. There is another class produced by the com- 
bination of a molecule of each form. The large number 
of hydrogen atoms to be replaced by metals in these com- 
pounds makes possible an endless variety of double sili- 
cates. The silicates form a large and important class of 
minerals, including feldspar and mica, which associated 
with quartz form granite, also hornblende, pyroxene, etc. 
Slate is a rock composed of silicates. The different kinds, 
of garnets are double silicates, the precious variety being 
a silicate of iron and aluminum. Topaz is an aluminum 






DMPOUNDG 0! SILICON, 

sil; titaining fluorine. Beryl is a beryllium-alumi- 

nuin silicate, and the emerald is a variety of it which OWBfl 

rich green oolor to a trace of chromium. Soap-stone 
1 meerschaum arc silicates containing irateroi oom 

tutinn. The clay which forms an important pari of the 
.. and different kinds of which arc used for making 
brick and porcelain. consists of powdered rilicates. With 
fc\s tiona the sili re fusible, and insoluble in 

water. Those containing water of constitution (hydrous 
Boomposed by all acids; the anhydrous Sili- 
cates are decomposed only by hydrochloric acid. 

344. Haloid Compounds of Silicon. — Foul atoms 
h of the halogens unite with one of silicon. 8ilu 

SiCU) may be prepared by burning silicon 
in chlorine. It is a transparent, punircnt, colorless, very 
stile liquid, 1 ►< »i l i mr at 59 I . Water decomposes it 
into hydrochloric and silicic acida s trafluort 

i> ). mav be prepared by heating to- 
ier Bilica, calcium fluoride, and sulphuric acid : 

- 2H,S0< = 8iF 4 H . II o. 

It is a heavy, colorless, fuming gas, of 3 # 8 specific grarity. 
When passed into water it is decomposed frith the forma- 

«.f rili< ..which separates as a gelatinous ma--, 

and a peculiar compound known ae hydrofluosilicic acid, 

which remains in solution : 

- + lll.o = I .'II SiF* 

are also other compounds in which two at. • 
of - f a halogen. It also forms a 

SiS,), v pound oi 

345. Glass. Wh.-n a mixture of qi 

and lin. it fuses ' liquid, 

wh isses thro 

•:. Win:- into obj( 



206 DESCRIPTIVE CHEMISTRY. 

any desired shape, which retain their form and transpar- 
ency when cold. This is common glass, a hard, practically 
insoluble, non-crystalline, and very durable substance. 
These many important properties, together with its cheap- 
ness, make glass fit for an endless variety of uses, and it is 
therefore one of the most valuable materials which man 
has at his command. Objects made of glass range from 
the great plates, fifteen or twenty feet long, which form the 
largest store-windows, to the delicate threads called spun- 
glass, which are as thin as the finest hair, and from the 
dirty-green or brown coarse bottles to the wonderfully clear 
lenses of the astronomer's telescope. All the hues of the 
rainbow may be given to glass, which marvelously increases 
the beauty of the objects that can be made from it. 

Glass is slightly acted on by water, especially in the 
form of steam ; solutions of some salts also dissolve it, and 
alkaline solutions corrode it still more. 




Fig. 126.— Glass Melting-Pots. 

346. Varieties of Glass. — Glass is chemically a complex 
silicate of an alkali metal, usually sodium or potassium, 
and some other metal, commonly calcium or lead ; it may 
contain three or more metals. Silica is the principal in- 
gredient, forming from half to three fourths of the bulk 
of the different varieties of glass. Each of the other in- 
gredients influences the properties of the glass, so they are 
chosen, and the quantity of each determined, by the pur- 
pose for which the glass is intended. Soda makes glass 
brilliant and fusible, and gives it a greenish tinge, seen on 



GLASS 



aw 



the edge of winriow-<;lass ; potash Lrivea no color to irhiSS, 

: less brilliancy and fusibility than soda; lime dimin- 
ishes fusibility and increases hardness and luster; lead 
fusibility and luster and diminishes hardn. 

If a perfectly odorless glass is wanted, soda can not he 




Via. 197 



used, and any impurity in the materials that would color 
product must he guarded against 
Window-glass is made from white Band, chalk (calcium 
mate), and soda-ash (sodium carbonate); a quantity 

of broken irlass, called - cutlet,* 1 ifl also added to make the 

mixture melt more readily. The chalk may he partly or 
wholly replaced by slaked lime (calcium hydrate), and the 

-ash by salt-cake (sodium sulphate). As the -and 

ontains a little ferrous oxide, which would oolor 
the glass green, an oxidizing agenl is added to convert this 
to ferric oxide, which nly a faint reddish t i 1 1 «_r< ■ that 

is not ble. Bottts-glass is made from common red 

. which contain- much oxide of iron, bei 

I is also one of its materials, hem • tains 

minum. 

ie ground Hint was formerly 
used in maki rtaimium load 

of lead used makes thi- 

Lille tile. 



208 DESCRIPTIVE CHEMISTRY. 

its power of refracting light as to render it very brilliant ; 
the lead makes this glass very heavy. Flint-glass, also 
called " crystal," is used for the finer kinds of glassware 
and for the lenses employed in optical instruments. It 
melts easily, and does not resist chemicals well. Flint- 
glass containing 53 per cent of oxide of lead forms what is 
called paste, which, from its brilliancy, makes a good imi- 
tation of gems. If uncolored it resembles the diamond, 
by the addition of a trace of ferric oxide the yellow of the 
topaz is imitated, and by cobaltic oxide the brilliant blue 
of the sapphire is produced. 

Bohemian glass is a potassium-calcium silicate. It is 
very hard, and is valuable for resisting heat and the action 
of chemicals. The glassware of chemical laboratories is 
made of this variety. 

Crown-glass is named from its mode of manufacture. 
It is used for window-panes and many other articles. If 
intended for optical purposes, it contains no soda ; some- 
times a little borax is used in place of a part of the silica. 

Colored glass is produced by the addition of small 
quantities of certain oxides of metals. Thus cupric or 
chromic oxide gives an emerald-green color, cuprous oxide 
a red, gold oxide a brilliant ruby, uranic oxide a yellow, 
oxide of cobalt a deep blue, manganese dioxide a violet, 
and a mixture of cobalt and manganese oxides a black 
glass. Powdered charcoal colors glass a brownish yellow. 
White enamel, used for watch-dials and other purposes, is 
glass rendered white and opaque by stannic or antimoni- 
ous oxide. " Flashed " glass has only a thin coating of 
colored glass on one side, added by dipping the ball of 
clear glass into liquid colored glass while it is being blown. 
For painting on glass, the article to be ornamented must 
be of glass that does not melt easily, and the paints consist 
of various metallic oxides, mixed with a powdered, very 
fusible glass, and turpentine. After the colors have been 
put on, sufficient heat is applied to melt the fusible glass. 






MBIALa 

■in is prepared by beating suitable 
kind- - aearly to the melting-point, and then dowly 

OOOling, by which they are math' while and \erv hard. 

The change ia due to the Beparation and crystallization of 

• silicates of the alkali metals are Bolnble in boiling 

. or soluble <rlass, used in fresco-paint- 

ementing broken glass and porcelain, and in the 

manufacture of >ilicated BOapS, is made from Band, BOda- 

ash, and charcoal, and consists of a mixture of Bodinm 
silicates, chiefly the tetrasilicate. 



DIVISION [L-METALS. 



347. General Character of Metals. — As stated on | 

106, the division of the elements into metals and uon- 

- only a rough classification for convenience. 

semble each other quite generally in the follow- 

properties: They are L r <">d conductors of heal and 

re malleable, and have a peculiar shine called 

the metallic luster; they form basic oxides, and, when 

tted from combination with non-metals, they appear 

at tie ole of the battery, hence they are Baid to 

|f( bals are not soluhle in any liquid. 
in acid 
.nd few of th.*m form compounds 

sli in different degrees, and w 

i is present in all metali and in all 

the Mining pages, i thai resemble each o( 



210 DESCRIPTIVE CHEMISTRY. 

closely are treated together in groups, which do not always 
agree with those of the Periodic Classification. 

The color of most metals is some shade of gray, but 
gold and barium are yellow, and copper is red. Many 
metals crystallize in the monometric system, others in the 
rhombohedric or the hexagonal system. The conductivity 
of metals for heat and electricity varies greatly. If the 
power of silver for conducting heat is rated as 100, that of 
copper will be 74, of iron 12, of lead 9, of bismuth 2, etc. 
For electricity the conducting power of silver and copper 
is five times as great as that of iron or platinum, and twelve 
times that of lead. 



CHAPTER XVII. 

GROUP 1 — THE ALKALI METALS: LITHIUM, SODIUM, PO- 
TASSIUM, RUBIDIUM, CJESIUM. 

348. The metals of this group are univalent. They 
are distinguished by a strong affinity for oxygen, which 
prevents their occurrence in the metallic state in nature. 
Some of them will float upon water, and the others are 
but little heavier. Their hydroxides are the strongest of 
the bases, and are called alkalies. Their compounds are 
nearly all soluble and alkaline. 

§ 1. Lithium. 
Symbol Li. Atomic Weight, 1 ; Quanti valence, I ; Specific Gravity, 0*59« 

349. The oxide of lithium (lithia) was discovered in 
1817 by Arfvedson, and the metal was first obtained by 
Davy. Although widely distributed, lithium salts occur 
in very small quantities only. They are found in milk 
and blood, in tobacco, in mineral waters, and several min- 
erals. They are usually obtained from the minerals triphy- 



90DIUM. 211 

hich contains lithium phosphate, ami Lepidolite, 

kiiul of mica. Lithium ifl soft, silver-white, ami is the 

lightest of all metals. It ami its compounds ooloi flams a 
tatiful crimson, and this observed by the speotrosoops 
bs a bright red line ami a lesi di-tim-t yellow one. 

The least traces of lithium may he dia- 
red in this way, 

impounds <»f this metal are mostly soluble, <leli- 
soent,and fusihle. They are used in medicine for goal 

; other diseases on account of their power of dissolving 
uric acid. The carhouate and phosphate are only slightly 

s. -.'. Sodium, 

fljjiiy m). Atonic Weight, 28 ; Quantivalence, I, Specific 

(.r;ivity, 

350. Preparation and Properties. — Metallic sodium 
was first obtained by Haw in 1807, by decomposing so- 
dium hydra! II ) by the el< 
tri<* current. Sodium does not 
OT native, hut is now manufact- 
ed on a large scale by distilling 
an of sodium carbonate or 
hydrate and charcoal at a higfa 
perafcure. Sodium, when fresh- 
ly cut, : a silvery appee 

If cast U] • runs W\ .rsodi. 

it on the Borfa ng by- 

is converted into sodium hydn 

+ 8H,0 8NaOH .- II.. 

If the water i- hot. p( from UHH 

«»f filter-paper, the hydn 

. which : : a brilliant jeUoi bj the 

metal. This yellow color is a test whicfa revee mall- 

est tra^r i , m. Observed ; 




212 DESCRIPTIVE CHEMISTRY. 

a flame shows a bright yellow line (Frontispiece, 5). 
Compounds of sodium are common ingredients of rocks 
and soils, and are found dissolved in mineral springs and 
sea-water. They are also found in many plants. The 
most abundant is rock-salt, and others are saltpeter, borax, 
and various silicates. Hardly a vegetable or animal sub- 
stance or bit of dust can be put into the gas-flame without 
giving the yellow sodium color, which is generally due to 
the presence of the chloride. Sodium is a soft, silvery- 
white metal, which melts and vaporizes at low tempera- 
tures. It is used in the extraction of the metals aluminum 
and magnesium from their ores. 

351. Sodium Hydrate, NaOH (Caustic Soda). — This 
compound is obtained by decomposing a solution of so- 
dium carbonate (Na 2 C0 3 + H 2 0) with calcium hydrate 
(slaked lime, CaH 2 2 ) at the boiling temperature, allow- 
ing the calcium carbonate formed to subside, drawing off 
the clear solution of sodium hydrate, and concentrating 
by evaporation. It is also formed by the action of sodium 
upon water, as described above. Sodium hydrate is a 
white, opaque, brittle substance, which melts below red 
heat, and volatilizes at higher temperatures. It deli- 
quesces in moist air, and its solution absorbs carbon diox- 
ide from the air. It has a caustic action on the flesh. Its 
chief use is in soap-making. 

352. Sodium Chloride, NaCI (Common Salt). — This 
substance may be formed artificially by burning sodium 
in chlorine gas. It occurs very abundantly in nature as 
a mineral (rock-salt), and dissolved in the water of many 
springs and lakes, also in the water of the ocean, which 
contains about four ounces in a gallon. The commercial 
supply is obtained from all these sources. Nearly all the 
countries of the world have sources of salt within their 
limits. The most famous deposit of rock-salt known is at 
Wieliczka, in Austria. It is estimated to be 500 miles 
long, 20 miles broad, and 1,200 feet thick, containing salt 



SALT MAKIN 

enough to Bupply the entire world for thousands 
The mines in this locality form a labyrinth of pa& 
and lofty chambers on different levels, having a 

nie of t ho chambers is fitted 
up as a chapel, its altar, . columns, pulpit, etc, be- 

ing all of salt. Among the l>est-known salt lakes arc the 
Dead Sea: I Salt Lake, in Utah; and Lake [Jrumiah, 

Salt exists In small quantities In plants, and 
their growth is sometimes aided by applying a little to the 
soil, though a large quantity kills most plants. It is 

found in all the BOlids and fluids of the bodies Of animal.-, 

and hence neither men nor beasts oao do without it in 
their food. Sorses and cattle that do not get salt often 
show the greatest >r it ; wild animals will travel 

long distances to spots where they can lick up earth con- 
taining salt. Such }»laee- are called u salt-licks," and are 
numerous in Kentucky and neighboring 8 Human 

found the craving for salt to be comparable 
with the pains of thirst and starvation, and li. 

will ;v enormous sums for a small quantity. 

353. Salt-making.— Most of th< S and Territoi 

of the Tinted States have salt supplies of their own. In 

lss; the quantity produced in this country was ; 
barrels, of which one half was manufactured in Michigan 
and nearly one third in (Jew Fork. Th- Is in this 

country generally lie several hundred feet below thi 
face of the ground, and are reached by boring. The weD 
is lined with an ii having a smaller pipe inside it. 

Water is allowed to run down in the larger p 
dissolves the the bottom, after which the brine 

d up throe inner pipe, and the salt is 

• • as froi 

iiL r out the salt than 
iike coal. The brine is 

- bj r-team- ; 

out, 



214 



DESCRIPTIVE CHEMISTRY. 



called " bitter water," or " bittern," contains chlorides and 
sulphates of potassium, calcium, and magnesium, and sul- 
phate of sodium, also bromides and iodides, some of which 
are extracted. The greater part of the sulphate of calcium, 
however, crystallizes before the salt does. Traces of these 
substances are to be found in most salt as it reaches the 
market. The chloride of magnesium is deliquescent, and 
by attracting moisture from the air causes our table-salt 
to become moist in damp weather. 

354. Properties. — Chloride of sodium dissolves readily 
in cold water, but, unlike most substances, it is only a 
little more soluble in hot water. It crystallizes in cubes, 
which are transparent and colorless, the red or yellow 
color of unpurified rock-salt being due to oxide of iron. 
A peculiar aggregation of crystals is often formed when 
the salt is allowed to crystallize from concentrated solu- 
tions. A small cube is first formed which sinks so as to 
bring its upper surface on a level with or a little below 



Fig. 129. 



Fig. 130. 




Fig. 131. 



Fig. 132. 




Fig. 133. 
Figs. 129-133.— Crystallization of Common Salt. 



the surface of the water (Fig. 129). Other cubes form on 
this, and, as the mass sinks, others still are deposited, 
each layer being attached to the upper and outer edge of 



•I'll M I kKBONAI gig 

iyer next below, until the bopper-like form shown in 
themoei diathennanous substance 

known — that is, heat passes through it most readily. 

355. Uses. Ball is u>ed u»r packing and presen imr 
meat, as it prevents putrefaction by absorbing from 
the flesh. It f sodium in the 
manufacture of sodium carbonate, and uree of ehlo- 
rine in the production of hydrochloric acid. It Fuses al i 
red heat and volatilizes at a still higher temperature, 

6 is need for <jlaziii£ earthenware. Salt is need BOme- 
what as a medicine. Salt water is BOmetil n to 

prodr iting. Baths in natural or artificial salt wa- 

ndered to be inyigorating. Applied to i 
1. it causes smarting and checks bleeding. Salt 
(1 part) and snow or broken ice (2 parte) form i 

mixt S • The Ball dissolves in the water from the 

nielti .ml the heat absorbed in the pro -<»lu- 

d from the bodies in oontad with the 

mixture. In the moet familiar use OJ _ r mixture 

— for freezing ice-cream — the cr e a m is put in ■ tin 
because the metal will eoiiduet heat from it readily; but 
the f: mixture surrounding the can is contained in 

a wooden tub to prevent heat being conducted in from 
drand melting the mixture too East Salt is often 
yinkled on sidewalks and street-railway tracks in i 

mow and ice upon them. The process depends 
on thf an remain liquid below the 

hieh pui 

356. Sodium Carbonate. im OOmpoui 
are supposed to perform the nme (unction in the i 

•in in land plants, and BOdiui 

was f- 1 by leaching the ashes of the former, 

mnd in tl 

It ; ,red from common salt 



216 DESCRIPTIVE CHEMISTRY. 

process. This consists, first, in treating sodium chloride 
with sulphuric acid, forming crude sodium sulphate or 
salt-cake, and hydrochloric acid. The next step is to 
convert the sodium sulphate into a crude carbonate. 
This is effected by heating the salt-cake with coal-dust 
and finely ground calcium carbonate (chalk) in a rever- 
beratory furnace constructed for the purpose. After the 
mass is thoroughly fused it is raked out into wooden 
troughs and allowed to cool, forming ball-soda or black- 
ash. In this operation, calcium sulphide and carbon 
monoxide are also formed, the reaction taking place ac- 
cording to the equation : 

Na 2 S0 4 +CaC0 3 + 4C = Na 2 C0 3 + CaS + 4CO. 

The sodium carbonate, being the only constituent of the 
black-ash that is readily soluble, is separated by leaching 
with warm water ; and, lastly, the solution is evaporated to 
dryness, yielding the soda-ash or crude carbonate of com- 
merce. When a hot, filtered solution of this is allowed to 
cool quietly, large transparent crystals of a hydrated salt 
containing ten molecules of water (Na 2 C0 3 , 10H 2 O) are 
obtained. These are known as sal-soda. On exposure to 
the air, sal-soda crystals effloresce — that is, lose water and 
turn white. 

Sodium carbonate is also prepared by what is called 
the ammonia-soda process. Ammonia and carbon dioxide 
gases are passed into a strong brine, by which acid sodium 
carbonate and ammonium chloride are formed. 

NaCl + H 2 + NH 3 + C0 2 = NaHC0 3 + NH 4 Cl. 

The acid sodium carbonate is crystallized out and is 
heated, when it gives off carbon dioxide and water, sodium 
carbonate remaining. 

Sodium carbonate has an alkaline taste and reaction 
and is very soluble. It is extensively used in the manu- 
facture of soap and glass, being both cheaper and purer 



SOW I'M SULFA I -JIT 

than the ordinary potash. It is washing 

calico-printing and in the laundry. II 

a coinnum name for it i> 

357. Acid Sodium Carbonate, Nall< 

-This a aturally in man] waters. It 

. in the ammonia-soda proeess ji. rihed, 

am! may be made also by passing carbon dioxide thn 

ition of sodium carbonate, [j is Less soluble than 

mate and has a less alkaline reaction. It is 

used in t-ookim: and in medicine for the carbon dioxide 

h it readily gives off uhm acted npon by almost any 

• bicarbonate 

of soda in one paper and cream Of tartar (arid pota88HUn 

in the other. When solutions of the two are 
i, a lively effervescence La produced by the carbon 
ae4 free, and Rochelle Ball is formed. The same 
e when " soda," as the bi •• is com- 

v called, and c tartar aiv ased for raising 

bread and rake. The carbon dioxide puffs up the d( 
B the little ca\ ities which when the I 

I ».ik lers contain bicarbonate of sods and 

aper one than cream of tar- 
mch as acid calcium phosphate. A mixture of alum 
and the phosphate is used in some powd< 

358. Sodium Sulphate. \ L0H,O {Qlaml 
i.— This well-known med by adding buI- 

phurie arid to common Ball in the lirsi -taL r -' 
process. It is also produced in the manufacture of nitric 

re. It has a hit- 
ter Ha 

[j solubility 
of the anhydr will di 

I but «ni 

1 It in used a.- a ; 
n called 



218 DESCRIPTIVE CHEMISTRY. 

359. Sodium Nitrate, NaN0 3 (Soda- Saltpeter). —Pro- 
cured native from parts of Brazil and Chili. Attempts 
have been made to substitute this salt for nitrate of potas- 
sium in the manufacture of gunpowder, but its tendency 
to attract moisture from the air has rendered this imprac- 
ticable. Sodium nitrate is the substance from which 
nitric acid is made, and it has been somewhat used as a 
fertilizer. 

§ 3. Potassium. 

Symbol, K. (Kalium). Atomic Weight, 39; Quantivalencc, I, III, and 
V ; Specific Gravity, 0*86. 

360. History and Occurrence. — This metal was discov- 
ered by Sir Humphry Davy in 1807. He first obtained it 
by subjecting moistened potash to the action of a power- 
ful voltaic battery ; the positive pole gave off oxygen, and 
metallic globules of pure potassium appeared at the nega- 
tive pole. It is found abundantly in nature, combined 
with various acids in animal and vegetable substances, and 
in many important minerals, chiefly silicates, also in min- 
eral waters. Potassium is obtained by the action of char- 
coal upon potassium carbonate at a very high temperature. 
The potassium carbonate is decomposed with liberation of 
potassium, carbon monoxide, and small quantities of other 

compounds but little known. Leav- 
ing these out of view, the reaction 
may be represented by the equation : 

K 2 C0 3 + 2C = 3CO + K 2 . 

361. Properties. — Potassium is a 

silver-white metal, and so soft at 

common temperatures that it may 

be molded like wax. If thrown 

fig. 134. - Combustion of upon the surf ace of water, instant 

potassium. decomposition takes place (Fig. 

134), potassium oxide being at first formed. The liberated 




LS8IXJ1 219 

a nil a small quantity oi volar, 
meta '.. tod by the heal evolved during th< 

. and burns with a beautiful lilac Same as the 
globule fl< .it on the surface of the liquid. At the 

close of ' »nd ehai \ the po- 

. which had bees kept above the Burfa 
ming in contact vrith the liquid, 
the formation of potassium hydrate, which becomes red- 
n ith a violent explosion. Potassium baa 
t>ng affinity for oxygen and decomposes nearl] 
compounds containing it if brought in contact with them 
at high temperatures, and many even a1 ordinary teni- 
ae, to preserve the metal from oxidizing, 
kept in naphtha, a liquid containing no oxygen. 
The am in a >alt may be ascertained 

by ti tint which it imparts to a gas-flame. In 

dium this tint is overcome by the yellow tint 
of the latter. The violet, however, becomes risible when 
Bame is looked at through blue <rlass, which absorbs 
yellow. I own in the frontisp 

gists of a violet line and two less distinct red lin< 

362. Potassium Oxide, K {P This com- 
pound is obtained I ising metallic potassium to 

tlv dry air. free from carbon dioxide, at ordinary 

a white solid, which melts 

er tern] 
deliquescent; brought in * with water it becomes 

tassium hydrate being prodn 

363. Potassium Hydrate. KOH (( ).— 

this im: 

Boda. The aolutioi 

potassium hy< i until the liquid 

without ebullition, i 
>, aolidif] ittle -u l»- 

below redness, t«. an oily liquid, 



220 DESCRIPTIVE CHEMISTRY. 

Potassium hydrate dissolves freely in water, with great 
evolution of heat. It has a peculiar nauseous odor and 
acrid taste, and is extremely caustic, rapidly corroding the 
skin. It is one of the strongest alkalies. It decomposes 
acids with formation of corresponding potassium salts 
and elimination of water, changes vegetable yellows to 
brown, and restores the blues discharged by acids. It is 
used in medicine to cauterize and cleanse ulcers and foul 
sores — hence its name, caustic potash. If a solution of 
potash is shaken in a bottle with any fixed oil, the two 
unite, forming soap. This accounts for the soft, greasy 
feel potash has when touched by the fingers, as it decom- 
poses the skin and forms a soap with its oily elements. 
It is a powerfully corrosive poison. Its active chemical 
character renders it an indispensable reagent in the labo- 
ratory. 

364. Potassium Chloride, KC1, is the mineral known 
as sylvite, and is isomorphous with common salt. It is 
found with salt in sea- water and in deposits in the earth. 
It is taken up from the water by sea- weeds and from the 
soil by certain land plants, especially beets, and is extracted 
from " kelp " and from the refuse of beet-sugar factories. 
It is largely used in making saltpeter (potassium nitrate). 
Potassium Iodide (KI) may be formed by adding iodine 
to a solution of a potassium salt, and gently warming until 
the solution assumes a brown tint. It is a very soluble, 
white solid, which crystallizes in cubes, and is much used 
in medicine. Its solution dissolves iodine, which is almost 
insoluble in water. 

365. Potassium Carbonate, K 2 00 3 . — Various potassi- 
um salts exist in the juices of plants. In burning the 
plants, most of these are converted to potassium carbonate, 
which may be obtained from the ashes. Wood-ashes, 
which contain from 20 to 50 per cent of this salt, are the 
principal source of the potassium carbonate of commerce, 
from which it is obtained by leaching them and boiling 



P0TAB8IUH OABBOfl 221 

:;timi to dryness in iron pots. The residue ig called 

I this, when calcined, IHfords the impure oar- 
Potash, or pearlash, th< 

ton «nta the readily soluble portion of \\ l-as] 

:i<ii\ of potassium carbonate with small 
amount ium carbonate and common salt Thii 

I highly alkaline, deliquescenl suit, and is used largelj in 

manofactui ap and glass, in preparing cam 

pol also an importanl reagenl in the labo* 

ostant presence of potassium salts in plants 
ind :at they are necessary substances in plant-food. 

has slmwn that U-\\ vegetables will thrive un- 
less there are potassium compounds in the soil, hence their 
le as fertilize 

366. Acid Potassium Carbonate. Kllrn , ,,,?/,■ 

-This is formed by passing carbon dioxide 

through a - solution of potassium carbonate. It is 

irce of potassium in the formation of 

many of its other compounds, and is ah tormaki 

g draughts, by adding citric or tartaric acid to 
solution. It was formerly used for raising dough, 
under the nam' ratue^ bu1 the cheaper sodium nil 

taken it = 
367. Potassium Nitrate, 1\\<> [Niter; Saltpeter) 

ive in the soil of farious districts in the 
[ndies, and is separated therefrom by leaching, and 
all' llise. It is artificially I by 

_ 1 1 1 i • - matter with animal od- 

ashes, and .,..•.! n. tin- 

roof, btii is moii om 

trie-draining - two or t ; 

i the sail i at 

> called made from sodium 

: potassium chloride . R< :• 

tain plants, lucb an- 

flo 



222 DESCRIPTIVE CHEMISTRY. 

times its weight of cold and one third its weight of boil- 
ing water. When thrown upon burning charcoal, it is 
decomposed and deflagrates violently. Paper dipped in a 
solution of potassium nitrate, and dried, forms what is 
known as touch-paper. When ignited, it burns slowly and 
steadily until consumed ; hence its use for fuses in lighting 
trains of gunpowder, fire-works, etc. Niter has a cooling, 
saline taste. Melted and run into balls it is called u sal- 
prunelle," and is a remedy for sore throat. Antiseptic 
powers are ascribed to it ; hence it is used extensively in 
packing meat, to which it imparts a ruddy color. It is 
chiefly consumed, however, in the manufacture of gun- 
powder, for its oxidizing power. 

368. Gunpowder is a mixture of about 75 parts niter, 
12 parts sulphur, and 13 parts charcoal. These proportions 
vary somewhat in different countries, as well as for differ- 
ent sorts of powder. More charcoal adds to its power, 
but also causes it to attract moisture from the air, which 
of course injures its quality. For blasting rocks, where a 
sustained force, rather than an instantaneous one, is re- 
quired, the powder contains more sulphur, and is even 
then often mixed with sawdust to retard the explosion. 
The niter used must be free from deliquescent potassium 
and sodium salts, which would cause the powder to become 
damp. The charcoal is made from light woods, such as 
willow and alder, because this burns easier than hard- 
wood charcoal. Distilled rather than sublimed sulphur 
is employed. The niter, sulphur, and charcoal, having 
been ground and sifted separately, are thoroughly mixed 
and then made into a thick paste with water. This is 
ground for some hours under edge stones, after which it 
is subjected to immense pressure between gun-metal plates, 
forming what is known as press-cake. These cakes are 
then submitted to the action of toothed rollers, whereby 
the powder is granulated. The grains of different sizes 
thus formed are sorted by means of a series of sieves, and 



POTASSIUM CHLORATE. 228 

ghly dried at a steam heat The (asi operation, that 

of polishing, is accomplished in revolving barrels, with 

vd irraphito, alter which the powder is ready tor 

urket The heavier the powder, the greater is its axplo- 

powder Bhould resist pressure between 

the fingers, giving no dust when rubbed, and have a 

j itlv gloss; aspect The explosive power of gunpowder 

is due to a sudden formation of a large volume of nitro- 

and carbon dioxide, which is greatly expanded by the 

i\ of tin' combustion, so that one volume of the powder 

BS about 3,600 Volun rases. Potassium earbonate 

I sulphate are the chief solids formed, hut other solid 

and gaseous Bubstanoes are also produced, so thai only a 

implicated equation could represent the ohanj 
which take pl.i 

369. Potassium Chlorate, KOIO* — This compound 
may he made by passing chlorine through a hot, strong 
solution of potassium hydrate, a- Bhown by the equation : 

BKOH + 3C1, = 5KC] + KC10, + 3H t O. 

It is a white solid, UOl very soluble iu Water, ami erystal- 

liziiiLT in six-sided prisma Like the nitrate of potassium, 

it ; oxidizing agent. If ;i few grains of the 

ehl< mixed with Bulphide <»t* antimony and the 

apped in a piece <•!' paper, it will explode when 

.<-k with a hammer. i lucifer-matrhi 

tipped with a mixture <»f these two rch, 

re lit by drawing them quickly through a folded 

i-ium «-hi-' much used 

iu «»f 

tasBium chlo 

i with sulphur and 
son. lie compound which will oolor t! • 

tinti mi 

nitrate green. Such m 

i 



224 DESCRIPTIVE CHEMISTRY. 

is also used as a remedy for sore throat. Its taste is like 
that of the nitrate 

370. Potassium Cyanide, KCK — This compound may 
be formed directly by heating potassium in cyanogen gas. 
On the large scale it is made by heating nitrogenous or- 
ganic substances, such as hoofs, clippings of hides, wool, 
and blood with potassium carbonate. It is a white, deli- 
quescent solid, very soluble and exceedingly poisonous. It 
is a powerful reducing agent, readily taking up oxygen 
when heated, forming potassium cyanate (KCNO). Its 
solution dissolves the sulphide and the haloid salts of 
silver, hence it is useful for cleaning silverware, and in 
photography and electroplating. Its properties also make 
it a valuable laboratory reagent. 

§ 4, Rubidium and Ccesium. 

Rubidium. — Symbol, Rb. Atomic Weight, 85*3; Quantivalence, I; Spe- 
cific Gravity, 1*5. 
Cesium. — Symbol, Cs. Atomic Weight, 133; Quantivalence, I; Specific 

Gravity, 1*9. 

371. Compounds of these two metals are found in very 
small quantities, usually with compounds of other mem- 
bers of this group in minerals and mineral waters. Kubid- 
ium has also been found in tobacco, tea, coffee, cocoa, and 
other plant products. Both metals were discovered in 
1860 by Bunsen and Kirchhoff, with the spectroscope. 
Kubidium was named from the Latin rubidus (dark red), 
because of the two deep-red lines in its spectrum, which 
also contains two violet lines ; and caesium, whose spectrum 
consists of two bright-blue lines, was named from the 
Latin ccesius (sky-blue). The other properties of these 
metals and those of their compounds are so much like 
those of potassium and its compounds that they need not 
be separately studied. This close resemblance makes 
separation of these substances exceedingly difficult. 



I VI. I U'M. 






CHAPTEK Will. 



>UP *:. — METALS OF mi: ai.kvi.im: EARTHS : I \i- 
l II M, STRONTIUM, B \ HUM. 

372. THESE are dyad elements. All an- somewhat 
heavier than water, and they deoompos tie- 
ally than the alkali metala The hydrates formed 

ible than the alkalies, bnl still have a dkaline 

chai 

g 1. ( 'alcium, 

i>o!, Ca. Atomic ^ uuitfomlenee, II tnd IV - 

ity, r.*»7. 

373. History. — Calcium was isolated by Maw in l- 

It is one of the mosl abundant constituents of the crust of 

the earth, being found in all spring and river waters, and 

forming tl of limestone, marble, and 

ilk, and I ll-fish, as a carbonate. Its sul- 

phal rpsum and alabaster, while as a ph 

phate it forms an important oon- 

the bones of animal-. 

• in all vegetables. 

The metal il 

native, but is prepared by pa* 
irrenl throng 
;m chloride. It is of a I 

. somewhat h;i 

py mallei 

D the 
air. It is rapid! by di- 

374 Calcium Oxide, I 
is well - known 

al- 

. in fu 

>fl by the 







226 DESCRIPTIVE CHEMISTRY. 

heat, and a white, chalky substance remains, called quick- 
lime, or caustic lime. When this is exposed to the air it 
first rapidly imbibes moisture and crumbles to powder. 
This gradually absorbs carbon dioxide, and, becoming less 
and less caustic, regains for the most part the neutral 
condition of the carbonate. The mixture of hydrate and 
carbonate thus produced is called " air-slaked " lime. 

375. Calcium Hydrate, Ca0 2 H 2 (Slaked Lime). — When 
water is poured upon quicklime intense heat is produced, 
the water boils and hisses, and clouds of steam rise into 
the air. The lime absorbs about one third its weight of 
the water, and swells to three times its original bulk, final- 
ly crumbling to a fine white powder, which is calcium hy- 
drate. This process is called "slaking" Sufficient heat 
is often produced by this chemical action to ignite wood ; 
barrels containing lime are frequently burst and set on fire 
if left exposed to a rain-storm, and vessels loaded with lime 
have sprung a leak and been burned at sea from the same 
cause. Lime-water is a saturated, transparent solution of 
calcium hydrate in water ; it is used as a chemical reagent 
and as a medicine. Cream or milk of lime is a thick mixt- 
ure of the hydrate with water, such as is used in white- 
washing. In tanneries the hides are immersed in milk of 
lime, which partly decomposes them, so that the hair may 
be easily removed. Calcium hydrate exhibits the proper- 
ties of a strong alkali, decomposing organic tissues and 
saturating the strongest acids. It is more soluble in cold 
than in hot water. Hence, when cold saturated lime- 
water is boiled, a portion of the hydrate is deposited. 
Slaked lime is extensively used in making mortar, cement, 
and the plastering of walls, for purifying illuminating gas, 
in paper-making, in chemical manufactures, and as a fer- 
tilizer. Its value as a fertilizer is due to the property 
which it has of decomposing organic and inorganic con- 
stituents of soil. 

376. Mortar and Cement. — Freshly slaked lime, mixed 



COMPOUNDS Of QALCIUM. ^^1 

with Band, forma the mortar employed by build 
cement and bricks. To make the best mortar, the 

lime should be perfectly caustic and the Band u sharp," 
that is, >f hard, _ rains. The change by 

which the moi - hardened, 1- not 

gplained. li i- supposed to be owing in 
sorption «»f carbon <li<>\i<ir from tin* air by 
the lime, and i quenl hardening alcium oar- 

In time the linn- also parti] combines with the 
ind, forming an exceedingly hard silicate of 
lima Common mortar, when laid in water, not only re- 
fuses to harden, but its lime gradually becomes dissolved 
• and washed away. Hydrauli the 

didifying under water. This quality 
_ •-» til.* presence of clay (aluminum silicate) in the 
linn* of which it is composed. 

377. Haloid Compounds of Calcium. — ( 

ing cha i ith hyd 

chl 1, and evaporating the ><»lnti<>n. I; iss wb 

- nt salt : • ml of it- Btrong attraction 

_ much used in the laboratory for dr] 

gMe& Crystals nf calcium chloride mixed with ice form 

a f: which will give a temperature of 

i. tli.- mineral J2 . is the 

from which all fluorine compounds are ma 
-ually found crystallized in cubes or other mono- 
bite "i* colored bright pun 
. or yellow . [t occurs also in 

the bones and h it light in the 

<lark when 

378. Bleaching - Powder Wln-n chl< passed 
tin- quantities of I 

are ah- 

ititution 



228 DESCRIPTIVE CHEMISTRY. 

calcium hypochlorite with calcium chloride, but it may 
correspond to the graphic expression Cl-Ca-O-Cl. It is a 
white, sparingly soluble powder, used in great quantities 
for bleaching cotton and linen cloth, paper-maker's rags, 
wax, paper, etc., but it can not be used for animal sub- 
stances. In the bleaching of cloth the goods are first 
freed from all greasy impurities and then steeped in 
a solution of this powder. They are next dipped into 
very dilute sulphuric acid, by which chlorine is liberated 
and exerts its bleaching power. This process requires to 
be repeated several times before the color is entirely dis- 
charged, after which the goods are thoroughly washed in 
water in order to remove all trace of acid from the fiber 
of the cloth. Chloride of lime is also used as a disinfect- 
ant (216). 

379. Calcium Sulphate, CaS0 4 . — This salt occurs na- 
tive as the mineral anhydrite, and, combined with water 
(CaS0 4 ,2H 2 0), as the minerals gypsum, alabaster, and 
selenite. It is slightly soluble in water, being one of the 
substances that cause permanent hardness. Its solubility 
is diminished by the presence of calcium and magnesium 
chlorides, but increased by dilute acids, 
common salt, and ammonia compounds. 
Gypsum is so soft that it can be scratched 
with the finger-nail. It crystallizes in flat 
prisms of the monoclinic system, which are 
as clear as glass if the mineral is pure, have 
a pearly luster, and easily separate into thin 
Fl sum 13 crystS yp " P^ a ^ es like m ica. A variety of gypsum is 
fibrous with a satin luster. Alabaster is a 
compact white or light-colored variety having a very fine 
grain. Owing to its softness it can be carved easily, and 
it is a favorite material for vases, statuettes, ornamental 
boxes, etc. Gypsum is much used as a fertilizer. When 
heated, gypsum loses its water, and then it may be easily 
ground to powder. Thus prepared it is known as " plaster 




iVUM CARHONATE 

of V.. 1 has the proper! combining witb 

rm a hard, compact mass, which expands in solidify- 

These properties maki' ii of use in forming m< 
ituary ami other objecl The plaal 

made into a paste with water, and the mixture is run into 

a hollow mold. The outside of the mass of pla>n 

urdens first, and, as the Bhell thus formed has the 
the mold which surround- it, whenever it lb pos- 
sible, the inner pari of the ma88 id QOt allowed to harden 

bat is poured out, thus making the cast hollow and much 
r than if it were solid. Plaster of Paris 1 for 

giving a " hard finish w to plastering, and mixed with glue 
and i for producing the ornamental designs known 

also an ingredient of various cements. 1 1 
left e to the air, plaster of Pfcris moisture 

and I - useless for easting. 

380. Calcium Carbonate, I at It >* — Vast deposits of this 

distributed all over the globe in the form of 

s, marbles, chalks, marls, coral It is 

chief mineral ingredient of certain hard substances 

ed in the bod animals, Buch as Bhells and 

d is found also in bones. The densest lime- 

i the softest chalk are found to consist of the 

aggregated skeletons or shells of myriads of low animal 

~, which h;: tied in some former period of 

•v. The rhich 

are sea-island lilt ap from the 

m by minute aquatic anim 
amp!- ilar dv\ -s of form; 

irl, which is the lining of tie- shell 

• mainly of the 
I alcium 
ingcarhoud: -o line '.hen it appear! 

<od as n test for the 
pre* 
ban 



230 DESCRIPTIVE CHEMISTRY. 

forms. It is soluble in water containing carbon dioxide, 
thus forming temporary hard water, from which it is de- 
posited when the dioxide is driven off. When water 
which has taken up a quantity of the carbonate in trick- 
ling through limestone rocks comes into the open air, 
such a precipitation takes place. In this way the icicle- 
shaped stalactites found hanging from the roofs of caves 
are formed and the stalagmites which are built up from 
the floor beneath. The carbonate is also deposited on the 
banks of springs and streams, covering sticks and grass 
with a hard, snowy crust, and sometimes forming masses 
of rock known as travertine, suitable for building-stone. 
St. Peter's Cathedral at Rome is built of it. Other varie- 



Fig. 137.— Double Refraction. 



ties of limestone, including the coarse and colored kinds 
of marble, are important building-stones, while the pure 
white, fine-grained marble is used for statuary. A variety 
of crystallized calcium carbonate, called Iceland-spar, has 
the remarkable property of double refraction— that is, of 
making objects seen through it appear double. Calcium 
carbonate is decomposed by acids with effervescence due 
to the escape of carbon dioxide, and this is one of the 
tests used for minerals. It is also decomposed by heat 
into carbon dioxide and calcium oxide (quicklime). 

381. Calcium Sulphide, CaS.— This substance may be 
prepared by reducing the calcium sulphate with carbon. 
It is white and insoluble, and has the remarkable property 



STRONTIUM. 281 

of being luminous in the dark after exposure to strongly 
tinic light Hence it Lb used in luminous paint for 
; r inL: match-boxes and other articles to make them \ iai- 
.1 night 

382. Calcium Phosphate, ( 'a, ( P< > 4 ) 8 . —This is the earthy 
aent of the bones of animals. They obtain it from 

plant.-, and the plants in turn take it from the soil. It is 

found abundantly in the grains of cereals, which, as the 

i>lv is limited in the soil, rapidly exhaust it when they 

are cultivated year after year. Senoe the importance of 

• the land in the form of tVmli 
when they are removed by the crops. 

g 2. Strontium, 

8ymt . S V' Weight, 87*5; Quant i\.l enc .II; Bpecific < i : avity, 

8-64. 

383. Strontium was discovered by Sir II. Davy, in 1 1 

nd snip: found as mineral.-. It 

How, malleable metal, which oxidizes on exposure 

air, and decomposes water at ordinary temperatures. 

It hums with a crimson flame. Its compounds, though 

less common, resemble the corresponding compounds of 

ium. 6 . is a deliquescent 

used in i red fire. 

Symbol. Ba. Atomic ) 

384. Barium was firsl obtained by Sir H. Davy, in If 

nu- 

• metal, which tai 
ordinary temperatures. It 

. Iditian 
ike- like lime, torn 

and 



232 DESCRIPTIVE CHEMISTRY. 

to adulterate white lead. Barium nitrate, Ba(N0 3 ) 2 , is 
used in making green fire. 



CHAPTER XIX. 

GROUP 3. — MAGNESIUM GROUP: BERYLLIUM, MAG- 
NESIUM, ZINC, CADMIUM. 

385. These are bivalent metals, volatilizing by heat, 
burning in the air to oxides, and decomposing water only 
when heated. Their oxides, hydrates, and carbonates are 
insoluble in water. 

§ 1. Beryllium. 
Symbol, Be. Atomic Weight, 9*4 ; Quantivalence, II ; Specific Gravity, 2*1. 

386. Beryllium, also called glucinum, was first extract- 
ed by Wohler, in 1828. It occurs as a silicate in beryl 
(whence its name), in the emerald, and a few other min- 
erals. It is a white, malleable, fusible metal, which does 
not burn in air or oxygen. Its compounds are colorless 
and sweet-tasting. 

§ 2. Magnesium. 

Symbol, Mg. Atomic Weight, 24 ; Quantivalence, II ; Specific Gravity, 

1-T4. 

387. History and Properties. — Magnesium was first 
obtained by Davy, in 1808. Its carbonate is found in 
nature as the mineral magnesite ; a double carbonate of 
magnesium and calcium is known as dolomite or mag- 
nesian limestone. As a silicate, magnesium occurs in 
mica, asbestus, hornblende, soapstone, meerschaum, etc. 
The sulphate and carbonate occur in most waters, and 
some of its compounds are also found in vegetables and 
animals. The metal may be prepared by decomposing 



, 



MAGNESIUM. 

gnesium chloride by sodiunL 1; Lb silver-white, hi 
it, malleable, and ductile, melting at a modera 
. jul volatilizing at higher temperatures, h d< ■< - • • ■ i a — 
poees warm l)iu nol iter, and doi e in air 

unless moisture is present Seated in the air it bui 
tzling light, to which it gives no color. [I 
much •«>unt ol the hi 

: artificial light in 
phy. 
388. Compounds. 1/ 
btained ugly heating magnesium carbonate. It 

. light powder, with feeble alkaline pro 
v sparingly soluble in water, but dissolving readily in 
[1 Blakes like lime, baryta, etc., bui produces little 
ride and hydrate are used principally in 
licine as mild aperients and antacids. ',' im 

M _ v « >.. 7H,0 5 i common 

of mineral waters, and tafc 
lined in quantities in the springs n 

gland. It occurs also as the minerals ep- 
somite and ki< rem which, and from dolomite, by 

the ilphuric acid, also from the hit* 

ial supply is derived. It is soluble in 
ias a bitter, saline taste, and is used in medicine 
a j» ".' M I | is found with 

n salt ii, ae deposits. [\ 

tallim- deliq table in water. It 

v double compoui at 

tmmonium, calcium, and other metals. 

8jTT: II 

389 History and Occurrence -This 



234 



DESCRIPTIVE CHEMISTRY. 



phide (blende), zinc carbonate (calamine), zinc oxide, red 
zinc ore, and a zinc silicate, are the most important. It 




Fig. 138.— Zinc Furnace. 

has been known for five hundred years, under the name 
of " spelter," by which it is still called in commerce. Zinc 
is obtained by converting its ores to oxides, from which 
the metal is distilled. It is a brilliant, bluish-white metal. 
At common temperatures it is brittle, but, when heated to 
100° C, it may be rolled out into thin sheets, and retains 
its malleability when cold. At 210° C. it again becomes 
quite brittle ; at 433° C. it melts, and at a red heat vola- 
tilizes. When strongly heated in the air it takes fire, 
burning with a whitish-green flame and producing zinc 
oxide. Zinc soon tarnishes in a moist atmosphere, form- 
ing a thin film of oxide, which resists further change. 
This property renders it useful for a variety of purposes, 
such as for bath-tubs, gutters, roofing, and for coating 
iron (wrongly called galvanized iron), thus preserving it 
from oxidation. Zinc is a substance of the highest impor- 
tance in modern industry. Mixed with other metals it 
forms alloys of extensive application (404) ; its power of 



iMPorxns ok zi\ L >:;;, 

cipitating other metals from solutions of their eom- 

B way of obtaining in a pure state copper, 

I, gold, silver, I >n account of its extremely electro- 

ther with its Ion price, it is indis- 

instruction of roltaic batteries for tele- 

phs, electric bells, and other par 

390. Zinc Oxide, ZnO.— This compound is formed 
when line Lb burned with Eras access of air. It is i Bne 
white powder, which turns yellow ou heating, but becomes 
white when cold. It is largely used as a paint, in place of 
white lead, under the name of u zinc-white." It is supe- 
rior in qoI being blackened by Bulphureted hydro- 

1 in not affecting the health <>f those who make 
and use it, but it is inferior in that it peels otT more easily. 

391. Zinc Chloride (ZnClt) may be prepared by dis- 
tilling an intimate mixture of rinc sulphate and sodium 

ehl<»ride. Zinc chloride is ■ whitish-gray tranaluoent sub- 

It melts easily and distills at a red 
vadily in water and al- 

ol. has a burning taste, and is poisonous. It is used in 

A manufactures, and for cleansing the sur- 

in Boldering. Wood, impregnated with a 

solution of sine chloride, is effectually preserved 

from decay, this process b Jled Burnettizing, By 

Le and chloride together a waxy substance 

ined, which is i filling teeth, and quickly 

392. Zinc Sulphate, X BO« ill ,0 < II ; 

• d either l». line sulphide at a 

m of sulphuric acid on me- 

I lee magnesium sulphate, to 

which il norphoo i a white, rfllnresenit silt, 

and . is an emetic, and in dyeing. 

impounds in s solution il ih< 
mlphide formed <»n the 
dition of ammonium Bulphid 



236 DESCRIPTIVE CHEMISTRY. 

§ 4. Cadmium, 
Symbol, Cd. Atomic Weight, 112 ; Quantivalence, II ; Specific Gravity, 8*6. 

393. Cadmium. — This metai was discovered in 1818. It 
does not occur native, but is found associated with some 
ores of zinc. It is a white, strongly lustrous metal, 
tarnishing in the air. It is soft, flexible, malleable, and 
ductile, melts at 315° C, and is volatile. In the air at 
higher temperatures it burns with a brown flame, cadmium 
oxide (CdO) being formed. Like zinc its molecule con- 
sists of but one atom. Cadmium in alloys makes them 
melt easier, without lessening their toughness or mallea- 
bility. 

Cadmium Sulphide (CdS) is a bright - yellow solid, 
valuable for making paint on account of its purity and 
permanence. The usual test for cadmium compounds is 
the .precipitation of the sulphide from solutions by sulphu- 
reted hydrogen. Cadmium Iodide (Cdl 2 ) is used in pho- 
tography. 



CHAPTER XX. 

GROUP 4. — LEAD GROUP. — THALLIUM, LEAD. 

394. Although the Periodic System does not place 
these two metals in the same vertical series, they are in 
many respects closely related. Similar in appearance, 
specific gravity, and atomic weight, they also form com- 
pounds which strongly resemble each other. 

§ 1. Thallium. 

Symbol, Tl. Atomic Weight, 204 ; Quantivalence, I and III ; Specific 

Gravity, 11 '8. 

395. Thallium was discovered with the spectroscope 
in 1861 by Crookes, in a deposit from the lead chambers 



LEAD 

a sulphuric-acid factory, traces of it being present in 

the pvi sulphur. Its sju'ctnun 

in intent en line | Frontispiece, 3), henoe 

■in a I treek word meanii t< is a heavy 

met r than lead, and melts even more easily. It 

rices a bluish mark on paper, which may be known from 

a lead mark by its turning yellow from oxidation. It 

f«»nns thai. _., T1C1) and thallic (e. g«, T1C1,) COm- 

g >. Lead. 

. _\ t < >i 1 1 i.* Weight, -J":; QuantWalenoe, II and 
IV ; Specific Grarity, 11*4. 

396. History and Occurrence.— Lead was known to the 
Lenta, and, at the time when the .-even known metals 

to have some relation to the seven important 
evenly bodies then known, lead was often called by the 
nan S el This useful and common metal is of 

ibtful occurrence, but is obtained from rariou 

ad sulphide) is the most important It 
i bluish, lustrous, brittle mineral with a cubical fracture, 
of lead- Found in the Rocky Mountains, 

and in Missouri, Illinois, and some adjoining States. 

397. Properties and Uses. — Lead is a Boft, blue metal, 
easily sratrhed by the nail, and lea* ing a stain whm rubbed 

upon paper. U is highly malleable, bul not very ductile. 
In the air a film of oxide rapidly forms on it- Kurfi 
which protects it from further n. It melts at the 

rathrr low temperature of 3 lolidifyii 

it unfit for i 
Lead is much used in the manufacture of p 

drinkinj dwell- 

gs. If had i^ exposed to the oombined action of p 

lir, plumbic hyd on the «\j»osed 

sur: ich is dissoh with which it is in 

of plumbic hydi 



238 DESCRIPTIVE CHEMISTRY. 

dioxide with formation of lead carbonate, a highly poison- 
ous compound. The presence of chlorides, nitrates, or 
ammonia assists this corroding action, while it is retarded 
by sulphates, phosphates, or carbonates. Calcium hydro- 
carbonate, found in many spring-waters, also prevents this 
corrosion by depositing a coating on the exposed surface. 
As all lead-salts are poisonous, there is always more or less 
danger in using water which has been kept in cisterns 
lined with lead, or which has passed through lead pipes. 
The service-pipes for water used in the household ought 
to be made of iron or tin. Where lead pipe is used, the 
water that has stood in it for a number of hours, as over- 
night, should be drawn off before any is taken for drinking 
or cooking. Lead in the presence of air and moisture is 
acted upon by feeble acids, even those in the juices of 
fruits and vegetables. Hence the use of earthenware 
having a lead glaze (428), or tin-ware made of "terne 
plate " (459), should be carefully avoided in cooking. 
For the same reason canned foods should never be allowed 
to stand in the cans after the cans have been opened, for, 
even if the tin is good, lead may be dissolved from the 
solder. Painters and factory-hands who use lead com- 
pounds are frequently attacked by lead-poisoning, but 
workers in metallic lead, as plumbers, are scarcely liable 
to the disease. 

Lead is extensively used in the arts, both alone and in 
alloys. Solder and pewter are alloys of lead and tin; 
solder may be one third, one half, or two thirds lead, ac- 
cording to what it is to be used for. Pewter sometimes 
contains other metals also. For type-metal, one part of 
antimony is added to four or five parts of lead, forming 
an alloy which is easily melted, and hard enough to resist 
wear. For making shot about one per cent of arsenic is 
added to the lead to give the shot the spherical form. Lead 
is not acted on by sulphuric acid at ordinary temperatures, 
hence its use for the chambers of sulphuric-acid factories. 



LB 0OMPO1 N 289 

398. Lead Monoxide, PbO {Plumbic Oxide). — Tbk 

a found native aa lead-ochre, a rare yellow min- 
eral. I tained on a large Bcale by heating lead to a 
it a littL -. "i* in the process <>f cupella- 
irmer product i> yellow ami is known 
J, the latter as litharge and has a red oolor. 
These are isomeric modifications. At a red heal lead 
i clear, dark-red liquid. In water it is 
able, with formation of lead hydrate. At a 
melting temperature the oxide combines with silica *<> 
form a lead silicate, henoe is much used in glass-making 
thenware. A mixture of litharge and 

bri< made into a paste with linseed-oil, forms a 

men! which sets ?ery hard. A solution of the oxide in 
lim< as a hair-dye It is very heavy, its gpe- 

; \ it\ being B 

399. Red Lead i 1/ (, -This substance occurs na- 
tive, and is so when massicot lb \'*>v some time 

< >sed to a low red heat m contact with air. It is ex- 
tent i> ;i pigment, iw a cement for iron pipes, in 

. and in the manufacture of Bint- 
_\..-. h i- a hraw bright-red solid, consisting of a mixt- 
ure • "f lead. 

400. Basic Carbonate of Lead, fcPbCOa. PbO,H t | White 

mbstanoe is manufactured in large quanti- 
ties,asit forms the body of nearly all paints used forooat- 
; wood, . I produoed in several ways, hut 

following, which is known ;i- the Dutch method, gi 
best product : I buckles M of sheet-lead, torn 

plaeed in earthen potfl with w. 

f the-e pot . 

tfa lead covers and closely pack then buried in 

spent tan-bark. 'I acid corrodes 1 1 rm- 

: lead a md the 

the <]< ible mal >m- 

poeei the aeetate with formation <»f bade lead carbonate 



240 DESCRIPTIVE CHEMISTRY, 

and free acetic acid. The acetic acid attacks more metal, 
which is again converted into carbonate ; and thus, with a 
small charge of vinegar, the operation is continued a long 
time, and a large quantity of lead is changed. White lead 
is extensively adulterated with barium sulphate ; it may be 
detected by adding nitric acid, which dissolves the lead, 
leaving the barium sulphate as an insoluble residue. 
White lead is a heavy white substance, practically insoluble 
in water. 

Paints for houses consist mainly of white lead and lin- 
seed-oil, with a little varnish to hasten the drying of the 
oil, and a little turpentine to keep the paint from getting 
gummy. The addition of small quantities of various com- 
pounds of metals gives such paint any desired color. 
Lamp-black produces black, but few other vegetable pig- 
ments are used by house-painters, as they are not generally 
durable. 

There is a normal Carbonate of Lead (PbC0 3 ) which 
is found in nature as the mineral ceriissite. 

401. Lead Acetate, Pb(C 2 H 3 02)2 {Sugar of Lead). — 
This substance gets its common name from its sweet taste. 
It is a white solid, readily soluble in water, and crystalliz- 
ing in prisms, the other lead compounds, except the nitrate, 
being practically insoluble. It is a salt of acetic acid, 
HC 2 H 3 2 , which is monobasic, hence one atom of lead 
takes the place of the displaceable hydrogen in two mole- 
cules of the acid. It is much used in the arts and in medi- 
cine, and is very poisonous. 

402. Tests for Lead. — All the salts of lead are precipi- 
tated from their solutions by iron or zinc. If a strip of 
zinc is hung in a solution of lead nitrate or acetate, it be- 
comes covered with a glittering mass of leafy crystals of 
lead, called the "lead-tree." At the same time zinc takes 
the place of the lead in the dissolved salt. The most deli- 
cate test for lead in solution is sulphureted hydrogen, 
which gives a black precipitate of lead sulphide {PbS). 



COPPER iM i 



OHAPTEB XXL 

VV 5. — COPPBB GROUP. — COPPER, KBRC1 BY, and 

>ll.\ BR. 

403. Tin: metals of this group arc bivalent, though 

►mpounds as CuCl, H ir^ K ami AgOl mighl incline 

ns to consider them univalent, silver, indeed, is frequent- 
ly a led,bu< the chemical deportmenl of these com- 

9 the conclusion that they contain two atoms 

of each constituent, linked as indicated in the formulas: 

Cu-ri Ilir-Cl -01 

(1 Ag-Ol A-Cl 

Unlike the two other metals with which it agrees in many 

resjw-cts, >il\er forms only one series of compounds. Oop- 

• and mercury gife ■ seoond series oontaining one atom 

ol metal only : 

I I . Cupric Chloride HgClf, If ercuric Chloride. 

l. Copper. 
Stt mm} Atomic w.-iL'lit, 6$*6; Q ttMti T t lcaoe, II ; 8p» 

Qrftfftj, 8*9. 

404. Production and Properties. — Thia metal, well 
known since the earliest times is often found nati\e in 

masses of considerable u& It ii obtained ou a large 

scale by tin ition of whi'-h copper py- 

3 4 ), cuproui oxide i ( and malachite 

. are among the inoM important. The |»roc»»>s 

* from its oxygen compound! I mi- 

: melted out when the I 

with charcoaL Ti. tkm of the metal from its >ul- 

difficult Large q 

mined about Lf 3 r and in the Mountains. 

II 



242 DESCRIPTIVE CHEMISTRY. 

Copper is hard, ductile, malleable, and of a red color. 
When finely divided, it burns, coloring the flame green. 
In dry air it is hardly acted upon, but in a damp atmos- 
phere it acquires a green crust of a cupric carbonate 
familiarly known as verdigris. Copper is an excellent 
conductor of heat and electricity, and is extensively used 
for telegraph-wires. Being little affected by the air, it is 
better adapted for cooking-utensils than iron. Vegetable 
acids, fats, and salt-water, however, act on it in the cold 
state; hence sauces containing vinegar, preserved fruits 
or jellies, and brine, should not be allowed to remain in 
copper vessels, as the salts produced are poisonous. Pickles 
colored green in a copper kettle owe their tint to a poison- 
ous copper compound. Copper forms alloys with other 
metals, which are harder than the copper itself . Among 
these are brass, consisting of 2 parts copper and 1 of zinc ; 
German silver, 5 parts copper and 3 of zinc ; bell-metal, 
7 parts copper and 2 of tin ; bronze, 20 parts copper, 1 of 
zinc, and 4 of tin. 

405. Compounds of Copper. — Copper forms two series 
of compounds, distinguished as cuprous and cupric, thus : 

Cu\ 
Cu/ 



X >0 or Cu 2 0. Cu = 0. 



Cuprous oxide. Cupric oxide. 

Cu-Cl /C1 

Cu-Cl or Cu 2 0L ° U \C1 or CuCl 



A 2 V^1 2 

Cuprous chloride, Cupric chloride, 

also written CuCl. 

Cupric oxide, CuO (Black Oxide of Copper), is found 
native as the mineral melanconite. It may be prepared 
artificially by strongly heating cupric nitrate, Cu(N0 3 ) 2 , 
3H 2 0. It is a black or brownish-black powder, melting at 
a red heat. When heated with organic substances, it freely 
gives off oxygen, which combines with carbon and hydro- 
gen, forming carbon dioxide and water. On account of 



mi:i;< tky 248 

thi- 'lie analysis. In the manu- 

facture ; U) impart ; 

. ifl found 
•lid, 

iss a line red color, 
5H,0 (//'•• J '/,'/•/ < ; k i> ob- 
snlphide in i nritfa air, <>r 

sulphuric a metallic It 

lution in beaatifal blue 

. and as a 
of many <-f ti 

Scheele's 1 by mixing boIu- 

Ii is of 

; as 
a }>: n. 

a liquids may he a- 

y immersing a bright knife-blade, which, 
I bj metallic . of 

f ammonia, which imparts an in- 
tense bine color. 

§ -• ] ' 

Symbol, I rjyrum). A* II; 

■ . 

406. History. n found 

ve in lit 
particular!} >hide (HgS). I 

.-••air liy di 

prith hurnt li 

[\ 
has a rilver-whil 

liquid at onlii 
gm ,a ball of irhich vril] 

float half immeraed in the liquid metal, while irood will 
float almost wholly ,di- 



244 



DESCRIPTIVE CHEMISTRY. 




Fig. 139.— Iron and Wood in Mer- 
cury. 



fies when cooled to —40° C, and is then soft and malle- 
able, but if reduced to a much lower temperature it becomes 

brittle. It boils at about 350° 
C, and slowly volatilizes at all 
temperatures above 15° C. Its 
vapors are poisonous. When 
pure it runs over glass without 
wetting it, but if impure it 
leaves a "tail," or trace. It 
corrodes all metals except iron 
and platinum. Metallic mer- 
cury is used extensively in the manufacture of philosoph- 
ical instruments, thermometers, barometers, and to form 
an alloy with tin for coating the backs of mirrors. It is 
also used largely in the extraction of gold and silver by the 
process of amalgamation. The alloys of mercury are called 
amalgams. A copper amalgam is used for filling teeth. 
Some amalgams are solid and hard, others pasty, and oth- 
ers liquid. Mercury is used in medicine as blue-pill, 
mercurial ointment, etc. Like copper, it forms two series 
of compounds, distinguished as mercurous and mercuric. 

407. Mercuric Oxide, HgO. — This substance, com- 
monly known as red oxide of mercury, or red precipitate, 
may be formed by heating metallic mercury above 300 C°., 
with free access of air. A still higher heat decomposes 
it, liberating the oxygen, and reducing the mercury to the 
metallic state. It is black when hot, and either red and 
crystalline or yellow and amorphous when cold. This 
oxide furnishes a ready source of oxygen gas, being the 
compound from which oxygen was first obtained by Priest- 
ley, and by which Lavoisier proved the composition of air. 

408. Mercuric Chloride, HgCl 2 (Corrosive Sublimate). 
— This compound is prepared by mixing mercuric sulphate 
(HgS0 4 ) with an equal weight of common salt, and ap- 
plying heat to the mixture ; the chloride, in the form of 
vapor, passes into a receiver, where it solidifies. (80.) It 



COMPOUNDS 01 KfKRGURY. -ji;, 

in water and in alcohol; its solution having an 

id, metallic taste, and an acid reaction. It is a deadly 

poison; the proper antidote is raw white ol egg, which 

rins with it an insoluble harmless compound. It is a 

liable du int, and is used as a medicine, also [or 

preserving wood by a process called " kyanizin_ 

409. Mercurous Chloride, II-,.( L r }. — This 

found native as u horn-quicksilver." 1 
1 by triturating mercuric chloride (HgClf) with 

- precipitated whenever Bolutions of any 

ndfl and a BOluble chloride are mixed 

together. Sublimed calomel is a crystalline mass, white 
i in color, insoluble in water, very heavy, taste- 
less, and inodorous. Calomel Lb decomposed by light It 
ttensively used in medicine. 

410. Mercuric Sulphide, HgS (( icurs in 
large !>♦ kimaden, in S ad Lb also found in i 

- in California. It Lb produced in consider- 
able quantity : ial means, and sold as a pigmenl 
under the d 

M re . addition of sodium hydrate, as- 

!is a yellow i>h one. 

i 

I 

411. Occurrence and Extraction.— This metal ! 

Dim from very early times; it- i:hai!im_r whiteness 

alchemists to think it had relationship 

with th . and they frequently called it by the same 

nan it h\ the -ame 

astr i | ine 

•ads, braneh. 

• s in n several hundred-weight 

with d an a sulphide, M ~il\« i 



246 DESCRIPTIVE CHEMISTRY. 

(Ag 2 S), as a chloride, "horn-silver" (Ag 2 Cl 2 ), as a sul- 
phantimonite, " dark-red silver-ore " (Ag 3 S 3 Sb), and in 
other combinations. The chief silver-mines of the world 
are in the Eocky Mountains, the Cordilleras of Mexico, 
and along the Andes in South America ; there are impor- 
tant mines also in the mountains of Spain, Eussia, and 
Germany, and deposits of more or less value in many other 
countries. 

An important method of extracting silver from its ores 
is the amalgamation process. The ore, first crushed to a 
coarse powder, is mixed with common salt and roasted, by 
which silver chloride is formed. This chloride, mixed 
with iron scraps, mercury, and water, is then shaken up in 
revolving casks ; the iron withdraws the chlorine, thus re- 
ducing the silver to the metallic state, when it becomes 
amalgamated with the mercury. This amalgam is then 
distilled, the mercury passing off and leaving the silver in 
the retort. 

The lead sulphide, galena, often contains silver, and 
after the mixed metals have been extracted from the ore, 
the silver is separated usually by cupellation. This pro- 
cess is conducted in a furnace, the shallow, basin-shaped 
bottom of which is covered with a thick layer of bone- 
ashes, marl, or some other porous, infusible material, form- 
ing what is called a cupel. When the lead, alloyed with a 
small quantity of silver, is melted on this hearth, in a cur- 
rent of air, most of the lead oxidizes. The oxide of lith- 
arge melts, and most of it is run off, the rest being ab- 
sorbed by the cupel, leaves the silver pure. 

412. Properties and Uses. — Silver is the whitest of the 
metals, with a bright, metallic luster. It is so malleable 
that it may be extended into leaves not exceeding 40V0 °^ 
a millimeter in thickness; and so ductile thafc T *g- of a 
gram may be drawn out into 180 meters of wire. Silver 
does not oxidize in the air at any temperature, but absorbs 
oxygen when melted, holding it mechanically, and giving 



PILVBR 

- the lu'st-known conductor of 
heat and electricity, and its polished surface is one of the 
be*' !' liirlu . It Lb harder than gold, but softer 

Hum copper. II melts at 1040 0., and it expands on 
lifying. Il-t Bulphuric acid co it to a sulphate, 

and dilute nitric acid toa nitrate. The sulphureted hy- 
drogen in the air tarnishes silver, forming upon it a coat- 

dphide <>f siher ( \ ■■;>). The L r a< niav he 

kept from sttvi ea no< in use bj wrappingthem in 

waxed paper. Salt also tarnishes silver, forming the chlo- 
ride sulphur in eggs and in India-rubber also pro- 

osumed in the manufacture of coin- 
age, rare, jewelry, Being too soft, pure >\\ 

purposes, bul is alloyed with 

i thirty per cenl oi copper, which greatly in- 

The proportions of the metals in 

alio for coii fixed by law in each country. 

In the Onil of the count ries of Europe 

. an* 90 of silver to 100 pari ich 

900 fine. The M standard silver,* 1 used 

nage and for most solid-silver articles in England, 

of silver to 75 pari tpper. The 

-t silver used in this country is called M sterling 91 sih 

and i inglish standard, though it 

differs somewhat with different manufacture 

madr from copper or 
some alloy i thin plate of silver, which i 

mac ■ opper a itfa 

• r nitrate and passing the Bheeta <»f metal '■■ 
rollers. 'I 

ilver up 

solution of 

to the | [wile. Mir- 



248 DESCRIPTIVE CHEMISTRY. 

rors are silvered by wetting the surface of the glass with 
a solution of milk-sugar or other organic reducing agent, 
and then with a solution of some ammonium-silver salt. 
The silver compound is reduced and metallic silver de- 
posited on the glass. " Frosted silver " is produced by 
heating the metal and dipping it in dilute sulphuric acid. 
The black tarnish on " oxidized silver " is really a thin 
coating of sulphide, formed by dipping the silver in a 
solution made by boiling together sulphur and potash. 

413. Silver Oxide, Ag 2 {Argentic Monoxide). — This 
substance is best prepared by mixing concentrated solu- 
tions of silver nitrate and potassium hydrate. It is a black 
or dark-brown, heavy powder, slightly soluble in water, its 
solution being feebly alkaline. When heated it is decom- 
posed, yielding metallic silver and oxygen. A solution of 
the oxide in ammonia deposits crystals of an explosive 
compound known as " fulminating silver." 

414. Silver Nitrate, AgN0 3 (Lunar Caustic). — This 
interesting substance may be obtained by dissolving me- 
tallic silver in nitric acid and evaporating the solution. 
Colorless, anhydrous crystals are obtained, which are 
readily soluble in an equal weight of cold water. These 
crystals, when melted and cast into small sticks, form the 
lunar caustic of surgery. Silver-nitrate solution is decom- 
posed by organic matter, with separation of black, finely 
divided metallic silver, the reaction going on most rapidly 
in the light. Advantage is taken of this property in 
making indelible ink and hair-dye. A solution of potas- 
sium cyanide removes the stain thus produced. 

Soluble silver salts are recognized by the white, curdy 
precipitate of silver chloride, which separates on the addi- 
tion of hydrochloric acid, and dissolves when the solution 
is made alkaline with ammonia- water. 

415 Silver Chloride, Ag 2 Cl 2 or AgCl (Argentic Chlo- 
ride). — This is one of the silver compounds which occurs 
in nature, the mineral being called horn-silver, from its 



rilOToiiKAlMIV. 



848 



horn-liko tc\tuiv. It may ln» pivpaml artificially 
by adding hydrochloric acid or a solution of Borne Boluble 
ohlorid . common Ball ) to a solution of a soluble >il- 

ter compound the nitrate). It is a vrhite solid, 

able in ammonia, in solutions of the thiosulphates, and 
and chlorides. 
■ ,.\ - . .\. .1 . like 

the chlorid< . ind in nature, and may be produced ar- 

tificially in a similar way They are both of a yellow <'<>l<>r. 
Th< soluble in ammonia, but readily soluble 

in a solution <»f sodium thiosulphate. These three haloid 
salts of sill remarkable for blackening on exposure 

to light ( hi tin- property the art of photography dependa 
416. Photography. — Photographic pictures are taken 
by means of th< a, an instrument in the form of a 

" - 

witli a tube, A I», 

pro 

front. Y h a thumb- 
lich the 

of the ! 

es apaii 

_Tound- 
glass ; pon 

which tin- image 
fori 
is seen by th< 

. who u thufl 1 to adjust the instrument properly 

Me changes in the position of the 
.• l. The back of the 
able, so thai the pi 
• 

i with 
lining a haloid • .u-hnh 

ition of in' 




140.- 



250 DESCRIPTIVE CHEMISTRY. 

silver. A haloid compound of silver is thus formed on 
the plate, which is then sensitive to the action of light. 
Accordingly, this must be done in a dark room, to which 
barely enough light to work by is admitted through a 
pane of red or yellow glass, which does not allow the 
chemical rays (96-102) to pass through, and the plate 
must be kept protected from the light until it has been 
put in place of the glass slide of the camera. The cap 
is then removed from before the lenses, and the light re- 
flected from the object to be taken falls upon the sensitive 
surface. Formerly it was necessary for the plate to be ex- 
posed in the camera and the sitter to remain motionless 
for twenty minutes ; but by using mixtures of various 
chemicals it is now possible to take a picture with an ex- 
posure of only an instant, and even to photograph ani- 
mals and other objects in rapid motion. 

When the plate is removed from the camera no change 
is visible, and another process is required to bring out or 
develop the picture. This consists in washing the surface 
with a solution of pyrogallic acid or sulphate of iron, 
which is done in the dark room. The silver compound 
has been so affected by the light falling upon it that it is 
reduced by the developer, and metallic silver in the form 
of a fine black powder is deposited upon the plate. On 
the parts that have received the strongest light, represent- 
ing the face of the sitter and light parts of the clothing, 
the silver is most easily reduced. These parts, therefore, 
appear dark on the plate, while dark objects appear light ; 
hence the plate is called a negative. When the picture is 
distinct enough on the negative, the developer is washed 
off with water, and the silver compound remaining unre- 
duced is dissolved out with a saturated solution of sodium 
thiosulphate so that no further darkening can take place. 

From the negative any number of copies of the picture 
can be printed. For this purpose paper is sensitized on 
one side by floating it on a solution of common salt, and, 



PHOTOGRAPHY, L >M 

- Iver chloride b 
thtu I on tfa A | of paper thus pre- 

ia placed under the negative and exposed to ran- 

it readily passes through the clear par:- ol 
ti<1 darkens the sensitive paper under them. 

Led }><»rti«>us, so 
that th< in the print are the of 

those in the negative and agree with those in the real ob- 

. n ia tak 
-at, nnl< kept away 

bom tii.- light, it will gradually blacken. Photograph 

Prints 
kepi from blackening bj washing oiri 

b chloride of silver with Bodinm thiosnlph 
ation an The print is next 

lation of chlorid _ Id, me- 
tallic gold in fib on the picti 

* tint. being washed and 

dried, the print I on a card and l> I or 

i by nibbing it with a smootl anient. 

in the pict- 
th a hard lead- 
ken on thin Bheet-iron 
directly— without making a i 
• kind of photognq 

Thl v took T :.- ■::• nam.' from I 

. who invented I 
m and made risible by a bl 
surface put behind them. 

Ine, 

it light in photograph 

er? 

dar- also fail 



252 



DESCRIPTIVE CHEMISTRY. 



black, and yellow specks in the face produce black points 
in a picture. It is obvious, from this unequal working of 
light, that many-colored toilets must produce discordant 
photographic results. 

417. Celestial Photography. — The applications of pho- 
tography in the arts are becoming constantly more valu- 
able, and it is also an important resource of science in 
making quick and accurate representations and in record- 
ing the workings of self -registering apparatus. Its astro- 
nomic indications are of especial interest. Enlarged pho- 
tographs of the moon represent the details of its surface 
with surprising minuteness, and photographs of the stars 
are taken which define their position with the greatest 
accuracy. In observing eclipses of the sun, this power of 

producing instanta- 
neous pictures is in- 
valuable, for the dis- 
play in a total solar 
eclipse is grand, com- 
plex, and momenta- 
ry — chromosphere, 
prominences, and co- 
rona, all burst upon 
the view at once and 
baffle every attempt 
at delineation. The 
corona, is a vast irreg- 
ular luminous ap- 
pendage surrounding 
the sun, reaching away to immense distances, only visible 
in eclipses, of unknown nature, and presenting the greatest 
diversity of aspects at different times. Photography is 
therefore eminently adapted to seize its peculiar and vary- 
ing appearances. Fig. 141 represents a picture of the 
eclipse of 1868 taken in a few seconds, and selected be- 
cause its aspect is very marked. 




Fio. 141.— Photograph of Total Solar Eclipse 
of 1868. 



ALIMINUM. 

OHAFTBB WII. 

>uf »'■.— 4 BRIUH GROUP. 

Yttrium, Y ,8 • - . I I nil Di Ivniium, 

Di . I LSD ; Kri.ium, Ki 

418. All the members of this group are wry rare. 
Tl oerally m silicates in oertain minerals oi 

arctic «ne are found in the United 

- tee. They are quadrivalent, but usually cuter into 

mpounds in the form of a double atom, which is i 
ivalent, thu 

I 
/\ /\ 

In propeitiefl tl mble the metals oi group ?, one <>f 

which, aluminum, will be fully described. They arc dis- 
tinguished from the aluminum group by the insolubility oi 

their oxalates and alums. They have no industrial 01 
. •(!• 7. — TH1 ai.imimm GROUP: alimimm, in- 

DI1 M. GALLIUM. 

419. T ds of this group, like those of group 8, 
are quadrivalent, the double atom being Bexivalent, as in 

Phe members of both groups form double sui- 
tes with the alkali metals, crystallising in regular 

oct^t died alums. The aluminum potassium 

Lmon alum. Whfii heated, all these metals 

decompose water an<l unite with its oxygen. 

420 Occurrence and Extraction \\ hil 

purposes, aluminuii 

soahundant in minerals, and is adapted to so many im- 
portant uses, that it is often called of the 



254 DESCRIPTIVE CHEMISTRY. 

future." This interesting metal was discovered by the 
German chemist Wohler, in 1827, It is not found na- 
tive, but its silicate is one of the most abundant minerals, 
forming the beds of clay, the argillaceous (clayey) rocks, 
and being an important ingredient of granite. Its oxide 
is the hard mineral corundum, and both silicate and oxide 
form important precious stones. Only two elements, oxy- 
gen and silicon, are more abundant in the mineral kingdom 
than aluminum. Every pound of common clay contains 
about a dollar's worth of this metal, but its extraction is 
very difficult. The usual ores of this metal are corundum 
(A1 2 3 ) ; cryolite, which is a sodium-aluminum fluoride 
found in Greenland ; bauxite, which is a hydrated oxide 
of aluminum and iron ; and kaolinite, its silicate. Alu- 
minum is mostly extracted by the method of Deville, who 
began his experiments ii\ 1854. A sodium - aluminum 
chloride is formed from the ore, by heating with carbon 
and common salt ; this double chloride is then heated with 
sodium, which displaces the aluminum from combination 
with the chlorine. The method has been much improved 
since Deville's time, especially by Castner's invention of 
an easy process for making the sodium employed. The 
Cowles process of extracting aluminum is a recent inven- 
tion, which consists in reducing the oxide by the intense 
heat of the electric arc. The electric furnace is a fire- 
clay box, in which huge carbon terminals are inserted. 
Between the ends of the terminals, a mixture of corun- 
dum, carbon, and copper is placed. As the aluminum is 
reduced, it is taken up by the melted copper, forming an 
aluminum bronze, which is afterward made of any desired 
composition. This alloy is one of the chief forms in which 
aluminum is used, and it is promised that the process will 
be made to yield pure aluminum. These and other im- 
proved methods of extraction within a few years have 
brought down the price of the metal from twenty dollars, 
or more than that of silver, to four dollars a # pound. 



nan op aij-mimm. 

421. Properties and Uses. -Aluminum is a shining 

J, of a shads between silver and platinum, 
der than rinc, and melts at i lower temperature than 
nol mated or tarnished by mois( 
sulphureted hydrogen. It Lb elastic, and is the 
• 3 h a clear, musical 

sound n >le and ductile, and ex- 

ceed in tenacity, while it is no heavier than glass or 

I \i conductor of heat and electricity, 

■: upon aluminum. It 

hydrochlori forming aluminum chloride, 

litun hydrate solutions producing 

oorresponding aluminates. Aluminum and its alloys are 

used for small weights and the beams of fine balan< 

for the tra ad parts of survej 

.and other instruments which it is important to 

hav as well as strong. Aluminum bronse, usually 

col f 90 part- copper and 10 parts aluminum, has 

• _ Id, and : ugth, together with its 

power of r :i. make it suitable for many 

important purposes. Aluminum brass, which is ehea] 

fuL An addition of a fraction of one per 
it of aluminum greatly facilitates the casting of si 
and make? it possible to cast WTOUght-iron. Aluminum 
does not am with mercury. 

422. Aluminum Oxide, Al<> m- 
ind forms a number of important minerals. In a p 

//////. which ' to 

1 in liar alar vai 

saie of iroi much na 

l colored by chromium, 
forms tl colored by cobalt, tie- napphin : while 

i with silicon a- ne. 

■pared art iti riuminum h the 

le i- a whit able in 

tasU oxide of allium. 



256 DESCRIPTIVE CHEMISTRY. 

423. Aluminum Hydrate Al 2 (OH) 6 . — The hydrate oc- 
curs in nature as Bauxite, one of the ores of aluminum, 
and several other minerals. It may be precipitated in 
solutions of aluminum compounds by the addition of am- 
monia. Thus formed it is a transparent, jelly-like sub- 
stance, and when dried at ordinary temperatures retains 
two molecules of water in its constitution, Al 2 (OH) 6 , 2H 2 0. 
When heated above 300° C, it loses most of its water, 
and is converted to aluminum oxyhydrate (A1 2 3 ,H 2 0). 
The hydrate absorbs so much heat in this process that it 
is used for filling the space between the walls of fire-proof 
safes. Another useful property is that of combining with 
certain organic coloring substances, forming pigments 
called lakes, and serving to fasten the color upon fibers 
that would not take it directly. 

424. Aluminates. — Aluminum oxide has weak basic 
properties, hence, as would be expected, it acts as an acid 
oxide toward stronger bases. This accounts for the exist- 
ence of a class of compounds called aluminates, examples 
of which are sodium aluminate (NaA10 2 ), used in sizing 
paper and as a mordant in dyeing ; magnesium aluminate 
(MgAl 2 4 ), which is the mineral spinel, a kind of ruby ; 
and beryllium aluminate (BeAl 2 4 ), which is the mineral 
chrysoberyl. 

425. Aluminum Sulphate, A1 2 (S0 4 ) 3 , 18H 2 0. — This 
substance may be formed by the action of sulphuric acid 
on clay, or aluminum hydrate. It is used as a mordant, 
and for giving weight to paper. 

426. Double Sulphates. Alums. — Common alum, the 
best known of these substances, is a Potassium- Aluminum 
Sulphate, K 2 S0 4 , A1 2 (S0 4 ) 3 , 24H 2 0. Small quantities of 
this important salt are found native, but for commercial 
purposes it is prepared artificially by several different 
methods. In this country it is formed by treating cryolite 
or clay with sulphuric acid, and, after a lapse of some 
time, adding potassium sulphate or carbonate. The whole 



alims. 857 

then leached, ind the alum separated from the solution 
hv . rvMaiii ;i;i..!i. Alum crystallizes in clear, color! 
cuhes or octahedra. It has a sweetish, astringent tac 
and is soluble in 18 parte of eold water, or in its own 
of boilil P. The solution has an aeid reac- 

tion, and d iron and zinc, Betting hydrogen free. 

It i< insoluble in alcohoL Alum is used largely for 

purifying and preserving skins, and as a source of alumi- 
num hydrate, whi.-h serves as a mordant in dyeing, for 
urifying * d liquors hv causing the impurities to 

and settle, and in medicine as an astringent and 

W 1 and cloth KMtked in alum solution will not 

asily, and hum very slowly. When quickly 

heated, alum d m its water of crystallisation, and 

part of tin- water is driven off, leaving a glassy solid; hut 

if heated slowly, all the wat.r may he driven otT, and the 
alum swells to a white, pOTOUi mass, called /////•/// alum, 

which i- insoluble and infusible. 

! I iMIj S0+A1, (S0 4 ) . -mii.(\ 

baring about the same properties as potash alum, is larj 
ly need for the same purposes. In its manufacture, the 
u ai! al liqu< gas-WOrks is nsed instead of a 

tvdum compound. The potassium may be replaced 

also by sodium, forming &odium ahum. Further, the two 
aluminum-atoms may be replaced by certain other met- 
als, SO that we have douhle sulphates containing iron, 

chromium, or manganese, and an alkali metal, which 
are also called alums, although they contain uo alumi- 
nu: re is -til! m of alum- in which leleni- 

um takes the place of sulphur, The alum- give s strik- 
trophism In color t ; 

me alum ii dark red, and iron alum 

427. Aluminum Silicates. — The douhle sflinatns of 
aluminum with other metals, such as iron, cah ium, mag- 
nesium, and sodium, are man] and of oomplii i sofep 



258 DESCRIPTIVE CHEMISTRY. 

ure. They form a large number of important minerals, 
including the feldspars and micas, which are ingredients 
of slate, gneiss, and granite rocks. Clay is simply the 
powdered material resulting from the decomposition or 
" weathering " of aluminous rocks. Pumice-stone is one 
of these silicates thrown out by volcanoes. The beautiful 
stone, lapis lazuli, used as a pigment under the name 
ultramarine, is one of these mixed silicates. The cause 
of its blue color is not certainly known. The substance 
is also made artificially. 

428. Pottery and Porcelain. — Clay when wet is so 
plastic that it can be molded into any desired form, and 
becomes hard and brittle on baking. Hence its fitness 
for making a great variety of useful articles. For porce- 
lain (china-ware), the purest variety of clay, called kaolin, 
consisting almost entirely of silicate of aluminum, is used. 
Silica and limestone are mixed with it in proper propor- 
tions to check the tendency of the clay to shrink in 
baking, and to make the mass partly melt, which gives 
porcelain the translucent quality that distinguishes it 
from, earthenware. The ingredients are carefully selected, 
ground fine, and thoroughly mixed. When molded into 
the proper form, the articles are dried, and then baked at 
a high heat in a furnace. After burning, the ware is 
called " biscuit," and, though hard, is porous, and absorbs 
water with avidity, even allowing it to filter through. 
Common flower-pots are biscuit ware. To prevent this, 
the articles are covered with a glassy coating, or glaze. 
This is put on by dipping them in a mixture of powdered 
quartz and feldspar suspended in water, and " firing " or 
baking them, by which the adhering powder is melted, 
forming a smooth, lustrous coating all over the surface. 
Fine porcelain is painted over the glaze. Pigments con- 
sisting of metallic oxides are mixed with a fusible glaze 
and applied by hand with a brush. The article is then 
fired again, which melts the pigment on its surface. The 



KNDIUK 259 

fin. is made in china, at Dresden in Germany^ 

wry, is i 
materials. I: is I under the gla pplyingthe 

ttern printed on paper bo the biscuit while the odor is 
the poro >rbed the color, 

the pa] - ut on, 

1 with Bali 

a dark color from impnril 

i with a preparation of clay 

bble for 

lometun Ived by 

nous effects. Bru is arc made of 

orned in piles called kilns. For some purp 

a glaze, which may be variously colored, is put on one 

. and Eessian crucibles, which 

ntaining much 

&, but f .•• red color of bricks and 

eoane pottery i> due l<» in»n compounds which arc oon- 
ride <»f iron in baku I un-colored 

in forms that can l" • ted 

Symbol, In. Atomic Weight, 1 

it>. 7 1. 

429. Indium by mean 

:' two bright lines— a hint- and 

found in zinc-ores. 

led as a dyad, u ith an :it< .ini«- 

found thai if ii«* 

old 

fill 

I* 
nui 
sof;> id. and 



260 DESCRIPTIVE CHEMISTRY. 

less easily by hydrochloric and sulphuric acids. It does 
not oxidize readily when heated, until redness is reached, 
at which it burns with a violet flame, forming yellow in- 
dium oxide (ln 2 3 ). From solutions of its compounds, 
sulphureted hydrogen precipitates the sulphide (In 2 S 3 ), 
which is also yellow. Indium forms an alum with am- 
monium. 

§ 3. Gallium. 

Symbol, Ga. Atomic Weight, 69 5; Quantivalencc, III; Specific Grav- 
ity, 59. 

430. Gallium was discovered with the spectroscope in 
1875 by a French chemist, who called it after the ancient 
name of France (Gallia). Its spectrum is two violet 
lines. Like indium, it occurs with zinc. It is a soft, 
silvery- white metal, which melts from the warmth of the 
hand, or at 30° C. Mercury is the only metal having a 
lower melting-point. If not disturbed, it will remain 
melted for many days, even though cooled to 0° ; but if 
touched with a bit of solid gallium, it quickly turns to a 
crystalline solid. It forms a white oxide (Ga 2 3 ), insolu- 
ble in water, also a deliquescent chloride (Ga 2 Cl 6 ), an am- 
monium alum, and other compounds. 



CHAPTER XXIII. 

GROUP 8. — IRON GROUP : MANGANESE, IROJST, COBALT, 
NICKEL. 

431. The chief feature of the members of this group 
is their variable quantivalence ; all of them are both biva- 
lent and sexivalent. The compounds in which they are 
bivalent resemble in structure those of the magnesium 
group, while the compounds in which they are sexivalent 
resemble those of the aluminum group. Manganese and 






KANGAN1 L v,i 

n, moreover, form compounds in which they appeal 

• alent atoms, and man<;ane> its as a 

tad. 

S 1 • ; 

Mil Aton VI utinknoe, II, IV, VI. vm ; Bpe- 

i 8. 

432. Occurrence and Properties, Compounds of man- 
ganese haw used from very early times to color 
glass, but I ined by Gahn in li- 
fts mpounds found in nature are several oxides, a 
solphid mate, and silicate, and it is widely distrib- 

_h it does not occur free. It is extracted by 
rides with carbon. Mangan* grayish, 

brittle metal, hard enough to scratch steel) and very diffi- 

cult to melt It <»\idizr> when exposed to the air, and so 
has- under naphtha. It decom] rater at 

mperatnres. A Bmall admixture of mangan 

increases the hardness of iron. 

433. Oxides of Manganese. — This metal forms five 
oxides: manga] ids (MnO), manganic oxide (Mn, 

.ranese tetroxide | M maniranese dioxide 

(MnO t ), and permai anhydride (Mn,<>.). The firs! 

i powerful base, the Becond is i weak base, the 

ither basic not acidic, while the last is an 

• important of them is 
(black oxide of mai >, which 

as t k soft mineral ind the somewhat 

in- 
posed, as shown I tion: 

5MnO f = Mn,o 4 + Of 

- used by chemists as a • n. It 

is also used in makimr chlorine from hydrochloric arid 

is also usee! I Jten material, but in large 

.ntitv it : • glass an amethyst tint 



262 DESCRIPTIVE CHEMISTRY. 

434. Manganates and Permanganates. — By melting 
the dioxide with potassium hydrate and saltpeter in a cru- 
cible, a green soluble solid is obtained, which is potassium 
manganate. Its formula (K 2 Mn0 4 ) implies that it is 
a salt of an acid of the formula H 2 Mn0 4 , but neither this 
acid nor its anhydride has been made. A solution of this 
salt, when diluted with much water, or on the addition of 
an acid, changes from green to purple. For this reason 
the manganate has received the name " mineral chame- 
leon." The change is due to the decomposition of the 
manganate, and the formation of potassium permanganate 
(K 2 Mn 2 8 ), manganese dioxide being precipitated : 

3K 2 Mn0 4 + 2H 2 = K 2 Mn 2 8 -f Mn0 2 + 4KOH. 

The formation of a green sodium or potassium manganate 
and its conversion to a purple permanganate, as just de- 
scribed, is a good test for the presence of manganese in a 
substance. By evaporation, potassium permanganate is 
obtained in rhombic crystals which have a metallic luster, 
and are of a dark-green color, except when the light shines 
through them, when they appear red. Its uses depend on 
its great oxidizing power ; as it readily gives up oxygen to 
organic substances, it is an important disinfectant. Many 
combustible substances take fire from the heat produced 
by its oxidizing action. Sodium, ammonium, barium, and 
silver permanganates may be formed in various ways. Per- 
manganic acid is known only in solution, but its anhydride 
(Mn 2 7 ) may be obtained, and is a brown, oily, unstable 
liquid, which decomposes, giving off oxygen at ordinary 
temperatures, and explodes when heated. 

§ 2. Iron. 

Symbol, Fe. (Ferrum). Atomic Weight, 56 ; Quantivalence, II, IT, and 
VI ; Specific Gravity, 1'8. 

435. History and Occurrence. — Were we to seek for 
that circumstance which might best illustrate the peculiari- 



IRON 

ancient and modern civilisation, we Bhould perhaps 
find it in the hu this metaL The ancients, imbued 

irith a martial spirit and passion Cor conquest, made iron 
the Bymbol of war,and gave it the emblem of Mars. And 
if i - • to symbolise the pacific tendenci 

triumphs of industry and rictoi 

of mind over n. . inonts and scientific 

old naturally employ the Bame metal, 
La _ rela have long been the type of bar- 

•. pomp, so ir<»n may now be well regarded 
as the emblei nl and intelligent industry. 

Small quantities of native iron are found in rocks and 
fall npon the earth as mel WTe are, however, ac- 

quainted with nun. of iron, of which the mosl 

important are the and hydrates (hematite, ma 

and limonite) and the carbonate (spathic iron and 
sulphide (iron pyi a very 

ral, but, as the other ores are easier to work, 
- not used as a * the metal. Other compounds 

found in many minerals. It is one of the m 
and widely diffused metal-. T! 

ydlow, brown, and black colors of rooks and soils, and the 

rati lore som on the surface of pudd 

are due to oxides and silicates of iron. It occurs in many 
mineral waters. Ohlorophyl (1 n coloring-matl 

and haemoglobin (the red coloring-matter of 

436. Extraction. -Nearly all the iron that we us 

in chimney-like 

lied hla es. These 

ait- 'i the mo.M refra 

■f the furnace » 

moke— il h door and i 

•••3 or tuyeres at tl. 
whi .in- 



264 



DESCRIPTIVE CHEMISTRY. 



ders driven by water or steam power. Formerly the air 
was used at the ordinary temperature (cold Mast), but now 




Fig. 142.— Blast-Furnace. 



an immense advantage is gained by heating the air before 
it enters the furnace (hot Mast), although the iron made in 
the old way is said to be purer. The furnace is supplied 
with alternate layers of ore, coal, and limestone, broken 
into small fragments. When the heat is sufficiently in- 
tense, the carbon of the fuel deoxidizes the iron, and the 
limestone being decomposed into carbon dioxide gas, 
which escapes, and " burnt-lime," which in its turn acts 



HtKPARATION OF WROUGHT-IRON •_>.;:> 

upon !• th the Band, day, and other impu- 

rities, to form ;; .a crude glassy, e&ffllj fn-i- 

The lime ia called a tlux, il helpc 

ma, irthy m id* The melted iron, sinking 

f the fur ^cumulates with the lighter 

sIbl .wn oil by taking oul a I 

[1 is . ,n into a bed of Band, containing a 

annel with ( branching oft a1 righl an- 

former is called by the workmen ti . and 

the latter the pig* ; hence the ban formed in them arc 

As tl of the furnace arc iv- 

low, ore, lin and fuel arc constantly 

plied from . md the operation goes on day and 

a, The ir<>n obtained by this pn 
known as cast-iron, suitable for casting. It 

irhon. There a 

irieties i . called white, gray, or mottled 

iron, dif in baring part or all of the carbon chemic- 

ally combined with the n | mir- 

M.-arlv pore tetraferric carbide 

437. Preparation of Wrought-Iron. — The oldest and 

niL r the 
with charcoal and a tlux. in an open tire urL r <-<! b 

-t. This i- • iron-smelting; and 

•ill in use in a f 3. With Buitabl 

an i .t qualil irly pure iron (wrooght-ir 

but at a grea of both metal ami fuel. 

rtion "f wrooght-ii 

purifvi: iron, which 

essential! hut also oontai 

iiijurioii 

-.lieoll. 

furnaces. In this process, 

the cast-inm ii the 

flat 'he 



266 



DESCRIPTIVE CHEMISTRY. 




Fig. 143.— Puddling-Furnace. 



furnace, as shown in Fig. 143. A workman, with a long, 
oar-shaped implement of iron, stirs the melted mass until 

the impurities are burned 
away or converted into a slag, 
and the metal becomes thick 
and pasty. This is called pud- 
dling. The puddler then rolls 
up from the mass a ball of 
about 75 lbs. weight, which 
he transfers to the tilting or 
trip hammer, where it is beat- 
en by heavy blows into a crude 
bar. By this operation the liquid slag, consisting chiefly 
of ferrous silicate, is squeezed out, as water is expelled 
from a compressed sponge. The metal, still hot, is then 
passed between grooved cylinders, where it is rolled out 
into bar-iron. The quality of metal is 
greatly improved when these bars are 
broken up, bound together, reheated to 
the welding - point, and again passed 
through the rolling-mill. This latter 
operation is often repeated several times, 
and is known as piling or fagoting. The 
puddling process has been largely dis- 
placed of late by the Bessemer process, 
which was first applied to the making 
of steel. Wrought-iron is so named because it can be 
worked under the hammer. 

438. Preparation of Steel. — Steel is between wrought- 
and cast-iron in the amount of carbon it contains, the 
usual proportion being about 1£ per cent. It may be 
made by adding carbon to wrought-iron or subtracting 
it from cast-iron. The former method consists in im- 
bedding bars of the best wrought-iron in powdered char- 
coal, in boxes or sand-furnaces, which exclude the air, and 
heating it intensely for a week or ten days. The chemi- 




Fig. 144.— Bessemer 
Converter. 



PREPARATION OF STEEL •_>.;; 

obscure; probably carbon monoxide pene- 
1 metal, i8 decomposed, surrenders pan of 

as carbon dioxide The steel when 
thdrawD has a peculiar rough, blistered appearance, and 

; sf,,/. This method <>f 
I l- call< [irnros. When this 

• into ingots, if com 
tntee ( . and when hammered to an even texture 

\ _:•• :.• improvement in the manufactured steel has 

laced, called from its inventor the B — mer 

process. \\\ means of tin-, steel ifl produced directly from 

the cast-iron, without previous casting into pigs and oon- 

t-iron. The melted oast - iron is run 

from the blast-furnace in1 shaped vessels made of 

, and lined with fire-clay, which are called 

r hich will hold from five to twelve 

-. An it of compressed air is forced into 

iten mass, and twenty to thirty minutes of this 

on suffice to hum off the impurities and convert 

the casl into wrought-iron. The addition of a 

ighed (pi leisen at the end of the oper- 

just enough carbon t<> convert the mass into 

439. Properties. I' n is of a sQver-white color, 

and wh< rfect luster. It is so malleahle 

tha* mad.- of it with leaves as thin as 

ind so ductile that it may be drawn out into wii 

'. itfa a magnet, or \\ I 
a curr* passed thro 

aro . hut on! 

•it has h 

red 1 1 i r has i 

bur. A \ is acted npness 

I dioxide and 



268 DESCRIPTIVE CHEMISTRY. 

iron to the carbonate. Heated in air, iron becomes coated 
with scales of the black oxide (Fe 3 4 ). It burns brilliant- 
ly in oxygen, and, when obtained as a fine black powder, 
it burns even on exposure to air. Chlorine, bromine, and 
iodine, in the presence of moisture, quickly corrode iron. 
Strong sulphuric acid has little action upon it, while the 
dilute acid rapidly converts it to sulphate, setting hydrogen 
free. Dilute nitric acid acts readily upon it, but if the 
ironis dipped in nitric acid of 1*45 specific gravity, it is 
not acted on ; and, if removed to dilute acid, the latter 
will then have no action on it, and it will not rust. The 
iron is then said to be in the passive state. This peculiar 
property is due to the formation of a thin film of black 
oxide (Fe 3 4 ) on the surface of the metal. It has been 
utilized in the Bower-Barff processes for producing " rust- 
less iron," in which the articles are coated with the oxide 
by heating them in superheated steam, or combustible 
gases and air. The usual impurities in iron as obtained 
from its ores are carbon, which makes it hard, brittle, and 
more easily fusible ; sulphur, which, even in so small a 
proportion as 0*01 per cent, makes it brittle at a red-heat 
or " red-short " ; phosphorus, which makes it brittle when 
cold, or " cold-short " ; silicon, which has about the same 
influence as carbon ; and arsenic, which lessens its tenac- 
ity and welding power. 

WrougM-iron is the purest of the three forms of the 
metal in common use, containing not over 0*5 per cent 
of impurities, mostly carbon. Its 
most useful quality is its great 
strength and toughness. So great is 
its tenacity that an iron wire -075 of 
an inch thick will hold up a weight 
of 449 pounds. Wrought-iron has a 
gray color and a fibrous texture, and 
rough, hackly fracture (Fig. 145). 
FlG * Wrou^hWr X on re ° f The effect of con stant jarring is to 







I USE [RON. 269 

ise it to I gh, fibrous character, and to become 

fstallina When wrought-iron is heated to whiteness,i1 

ft, pasty, and adhesive, and two pieces in this 

'ii may be incorporated, or hammered into one. 

This is call Daring the heating a film of black 

>rmed upon the surface of the metal, which 

struct the ready ooheeion of the separate mast 

this, the smith sprinkles a little Band upon the 

fmt iron, which gives rise to the formation of a fusible 

, easily forced ou1 by pressure, leaving clean sur- 

at anitewithoni difficulty. This importanl quality 

possessed only by iron, platinum, and sodium All the 

suddenly from the solid to Hie liquid 

te, at their respective melting-points. Wrought-iron 

doe* not melt until a bright white heat is reached. 

a granular texture | Fig. 1 M$), and is so 
brittle that it can nol be forged, bul may be remelted and 
cast in molds. I when fii 

>py it 
tently confa 
by the parti- 
assuming lline arrange- 

• while | the oon- 

q, by the cooling of the n 
tailic mass when Bolidift 

nihility of oasl - iron with the 
malleability <>f bar-iron, [ta falue for cutting instru- 

ds upon its capability ol being 

D heate ncss and suddenly mirm-l 

in Ldass. 

If again heated an 1 alowh . 

: i nary i: 

i degree «»f hardness i the 

the thin film of oxide U] 
its tlv changea in odor. 

ar» 




270 DESCRIPTIVE CHEMISTRY. 

the degree of hardness for razors ; if tempered at a deep 
blue, it becomes very elastic, and is suitable for sword- 
blades, saws, and watch-springs. Steel takes a higher 
polish than iron, and has less tendency to rust. Nitric 
acid corrodes steel, and leaves the carbon as a dark-gray 
stain ; hence it is often used for writing and ornamental 
shading upon this metal. Case-hardening consists in con- 
verting the outside of iron articles into steel by heating 
them with bone-dust or other substance containing carbon, 
and then cooling in water. 

440. Uses. — Iron in one of its three forms ministers 
in innumerable ways to the benefit of all. The imple- 
ments of the miner, the farmer, the carpenter, the mason, 
the smith, the shipwright, are made of iron and with iron. 
Eoads of iron, traveled by iron steeds, which drag whole 
townships after them and outstrip the birds, have become 
our commonest highways, and cross broad rivers or deep 
chasms by iron bridges. Ponderous iron ships are afloat 
upon the ocean, with massive iron engines to propel them ; 
iron anchors to stay them in storms ; iron needles to guide 
them, and springs of iron in chronometers by which they 
measure the time. Ink, pens, and printing-presses, by 
which knowledge is scattered over the world, are alike 
made from iron. Stoves, cutlery, machinery, gas- and 
water-pipes, cooking utensils, wire for a host of uses, the 
metal parts of our carriages and wagons, rifles and cannon, 
beams for buildings, and the great variety of nails, screws, 
and other hardware, are still other articles made from this 
most useful of metals. Of these things, those requiring to 
be elastic, or hard and very strong, are made from steel ; 
cast-iron is used for articles which must be made cheaply 
by the casting process, and in which brittleness is no great 
objection ; where the metal must be easily cut, joined, and 
shaped by hammering, or rolling, wrought-iron is used. 
Improvements in processes of steel-making recently dis- 
covered have made possible the substitution of this more 



axmn of mom 2:1 

durable form of the metal for wrought-iron for many pur- 
poses. Steel rails, steel >i. 1 wire for suspension- 

bridges, Bteel beams and girders, and steel oables, are in- 

441. Oxides of Iron. / i ■ ■ . FeO, is not found 
native, but ined when I ride 1- reduoed by 

g in dry hydrogen. It is a black powder, which in 
spontaneously, burning to ferric oxide. [I 
en. 
] I >- ( Red 
w ide distribution as the minerals red hem- 
Liar iron, from which a large proportion 
- derived* Ii forms rhombohedral 
in granular, fibrous, or earth-like 
masses, [ta color ia brick-red, and it ia the sul 
whieh colon bricks, red pottery, and many red rocks and 
soils. I; Ik IS hematite, and I , mixed 

wit": :v. H.inatite Lb extensively employed 

oolcothar and jewel< . - a pig- 

nd for } _ jewelry, glass, and metallic obje 

I-', ( >. i', ^ ) t 1 Magm tic 

-This substance native as the 

. tie- mod valuable of the ram 

whi It in la 1 is 

tly found in distinct octahedral nd- 

tic, and another of 

de which forms 

in- 
nd, which Lb also produ ion of ii 

442. Ferric Chloride, I I in dai 
scales, ( Hie aj .j - . when iron U beated u 

gas. I 
I 
account of ink 

matter, as a 



272 DESCRIPTIVE CHEMISTRY. 

443. Ferric Disulphide, FeS 2 . — This compound occurs 
native in two isomeric modifications, one, the mineral mar- 
casite, the other, iron pyrites. Both forms are widely dis- 
tributed. Iron pyrites crystallizes in cubes or other forms 
of the isometric system, of a golden-yellow color and strong 
metallic luster. Heated in the air, iron pyrites burns with 
evolution of sulphur dioxide, and it is much used in the 
manufacture of sulphuric acid. Sulphur and copperas are 
also obtained from it, but it is never worked for iron. 
Marcasite is a white mineral with a metallic, luster, which 
in moist air decomposes rapidly, with formation of ferrous 
sulphate and evolution of heat. It occurs in coal-beds, 
and sometimes causes their spontaneous ignition. 

444. Ferrous Sulphate, FeS0 4 ,7H 2 (Green Vitriol, 
Copperas). — This salt occurs native, and is largely manu- 
factured from iron pyrites, by exposing the mineral to air 
and moisture. It is used in dyeing, for making ink and 
Prussian-blue, for purifying coal-gas, and as a disinfectant. 
It is very soluble, and forms efflorescent green crystals. It 
often exists in soils to a pernicious extent, but is decom- 
posed by lime, gypsum being formed. Ferrous Carbon- 
ate, FeC0 3 . This is a very abundant mineral, known as 
spathic iron. It is grayish- white, opaque, and crystallizes 
in rhombohedrons. When found in large masses, it con- 
stitutes one of the most valuable iron-ores. Steel has been 
made directly from it, hence it is known as steel- ore. It 
is the usual iron compound in chalybeate mineral waters. 

445. Iron and Cyanogen. — When nitrogenous animal 
matter (horns, hoofs, blood, etc.), in presence of iron and 
in contact with air, are heated with potassium carbonate 
and the resulting mass is treated with water, this, on 
evaporation, yields large crystals of a yellow color, hav- 
ing the composition 4KCy.FeCy L ,,3H 2 0, and known by 
the name of prussiate of potash, or potassium ferrocya- 
nide. It is the source from which all cyanogen compounds 
are generally prepared, and is assumed to be the potassium 



tA^T. 278 

i. When to a >«»lu- 
the potassium Bali a e of ;i ferric Ball ii 

following 

:;k - \T, < i- 12KCL 

impound 1 • a- a dark-blue 

I >\. :; ..ri the yellow potassium ferro- 

inide into potassium ferricyanide (Krv<\.i. which 

3 mi red prisma \\ hen added t<» tin- solution <>f 

is salt, a blue precipitate is likewise obtained, but 

Deposition "f Prussian-blue : 

BE - Vr{\ I K6KOL 

Tli known by the name of TurnbuWs h 

r rh< (inns furnish an easy waj of distinguishing 

ferric from & The presence of a ferric Ball in 

a liquid can be ascertained with the utmost accuracy by 

assium Bulphocyanide, which produces a deep-red color. 

bait. 

}k>1, Co. Atomic W II and VI; Bp ec M fa 

Gravity, 8*6. 

446. The Metal.- Cobalt-ores bave been used for 
d hundn ooloring glass, but the metal 

i- derived 

from tl . applied t<. L r «»Min- which were Baid 

baunt the mini I armany. 'Ii 

ir in the free -' found alloyed n itb iron in 

I- . from orea, in which it ii oom- 

l>inr«l with sulphur 

I reddish o 

bat inai red 

dcei a li. 

lies in i r : the mini 



274 DESCRIPTIVE CHEMISTRY. 

when dilute, act on it readily. It has not been applied to 
any useful purpose. 

447. Compounds of Cobalt. — This metal forms two 
series of compounds, distinguished as cobaltous and co- 
baltic, and corresponding to ferrous and ferric compounds. 
Cobaltous Chloride (CoCl 2 ,6H 2 0) may be obtained in 
ruby-red octahedral crystals from solutions of cobaltous 
oxide or carbonate, in hydrochloric acid. The dilute so- 
lution of these is used as a sympathetic ink, the characters 
written with it being so pale as to be invisible till warmed, 
when they appear blue, owing to the formation of the an- 
hydrous chloride (CoCl 2 ). On cooling, they absorb moist- 
ure and again disappear. Smalt is a mixed silicate of 
cobalt and potassium. It is a bright-blue substance, used 
for coloring glass, and is made by roasting the cobalt-ore 
to change the metal to oxide, and then melting with sand 
and a potassium compound. The test for cobalt is to melt 
a little of the substance supposed to contain it with borax, 
to see if it gives the characteristic blue color. 

§ 4. Nickel. 

Symbol, Ni. Atomic Weight, 58*6 ; Quanti valence, II, IV, and VI ; 
Specific Gravity, 8*8. 

448. The Metal. — Nickel is found in nature with co- 
balt, not only in the sulphur and arsenical ores, but also 
in meteorites. It was discovered by Cronstedt, in 1751. 
These two metals are closely related by their properties. 
Their atoms have the same weight, and their reactions are 
so similar that there is difficulty in separating one from 
the other. Both resemble iron in many properties. Like 
cobalt, nickel is magnetic. It is a silver-white, ductile, 
and malleable metal, and does not melt much easier than 
iron. Alloys of nickel are used for making small coins in 
several countries — our five-cent piece is composed of one 
fourth nickel and three fourths copper. " German silver " 
is an alloy of about five parts copper, two of zinc, and two 



ohromiui 275 

of niokeL The effed of 1 1 1 * - nickel is to make these alloys 
hanl ami durable, and to give them a beautiful whiten 
almost equal to that of silver. Being {inalterable in the 
air. it is ro-plating other metals, 

esj>« . the Ball used being the potas- 

sium-nickel cyanide. 

449. Compounds of Nickel. Like oobaU and iron, 
vrl funns twn >< :•;-- <>f r<»iii)»oun«ls r. <;., nickelous 

\ « » i and oickelic oxide | N :. ( I .i. The presence of 
Icel com] may be detected by means of the 1 i lt h t - 

loos hydram ( Ni ( Ui s ), formed 
on I ition of potassium hydrate. 



CHAITKK XXIV. 

BROMIUM GROUP: ( BROMIUM, MOLYBDBH D M. 

Ti ET08TBK, \ M» I i;.\ N HM. 

450. Thbbi elements exhibil a variety of \al« -^ 

Th form acids analogous to manganic acid; 

ohr Kraipoun -1> conforms to 

sexivalent iron ; all members of thi group are quadrivalent 

lome of their compounds, and in others bivalenoeand 

quinqui d obsen 

'I Hi. 

1 1 . I \ ■ i \" I j 

451. The Metal I by 
I in, in 1 ", I i ml <-f the bl of 

i from tin- <ir««k \sm 

hut th»- metal and 
con 



276 DESCRIPTIVE CHEMISTRY. 

which consists of ferrous and chromic oxides. Another 
mineral containing chromium is " crocoite," which is a 
lead chromate. The metal may be obtained by subjecting 
chromic oxide to intense heat with charcoal, in a charcoal- 
lined crucible. It is of a steel-gray color, exceedingly 
hard, and very difficult to fuse. It crystallizes in octa- 
hedra. A small quantity in steel increases its hardness. 
Boiling nitric acid has no action on it, but hydrochloric 
acid and hot sulphuric acid combine with it, setting hydro- 
gen free. 

452. Oxides of Chromium. — No chromous oxide has 
been obtained, although a chromous hydrate (Cr0 2 H 2 ) is 
known. Chromic Oxide (Cr 2 3 ) occurs in nature, mixed 
with clay, as " chrome ochre," and also in " chrome-iron 
ore" (FeO.Cr 2 3 ). It may be obtained by heating potas- 
sium bichromate with sulphur, and treating the mass with 
water, which dissolves out the potassium sulphate formed, 
leaving the insoluble chromic oxide. This substance has 
a bright-green color, is insoluble in acids, and unaffected 
by heat. Hence it is used for coloring glass and porcelain, 
as well as in ordinary painting, under the name of " chrome- 
green." It gives the emerald its green color. Chromic 
Anhydride (Cr0 3 ) may be obtained by the action of sul- 
phuric acid on potassium bichromate. It forms splendid 
needle-shaped crystals, often an inch in length, which are 
deliquescent and easily soluble in water. It melts at 100° 
C, and decomposes at 250° 0., giving off oxygen, while 
chromic oxide remains. It is a powerful oxidizing agent, 
and is reduced by sulphur dioxide, sulphureted hydrogen, 
and most organic substances. It is used in bleaching 
certain oils. The ruby is thought to be colored by it. 

453. The Chromates. — The acid corresponding to 
chromic anhydride has not been prepared, but several 
salts of such an acid, or chromates, are known. Potas- 
sium Chromate (K 2 Cr0 4 ) is a yellow, crystalline, soluble 
solid, which changes to a red color on melting. It is 



MOLYRDENTM. 077 

made from chrome-iron ore by heating the mineral with 
issimii carbonate and chalk* If the resulting mas 
ed and treated with nitric or Bulphnric acid, Pa- 
- t !\ f Potasl \ 

formed, and may be separated by crystallising i 

:K.( p0 4 • 11 -<»_k ( ; n : | k vo ; . ii o 
dfl Bait formfi red trielinie erystals. Its solution 

in water has an acid reaction. It is an oxidising agent, 
and is need in calico-printing. 

454. Molybdenum, Mo, w; \nv<l by Iljelm, in 
178S _ht was formerly taken to be 92, 
but Mendelejefl predicted, from the arrangement oi the 

I sification, that it was really higher than that 
of niobium. This ha.- e<mtirme<l by experiment, 

and thi qow placed at 96. Molybdenum is a 

white, brittle metal, which does not tarnish in the air, 

infusih in the oxyhydrogen-flame, unl< 

the • txra. Its specific grai itj It 

forms moi . compounds, in which it Le a dyad, and 

molybdic compounds, in which it ia a tetrad. Ammonium 

in chemical analysis to form a precipi- 

with phosphoric acid. 

455. Tungsten, W ( Wolfram), was ol)taine(] by Sehi 

in 1781. It is a wMte, hard, brittle metal, which does not 
. md ifl almost inf Fire per cenl of 

it in steel d telj hard metaL l\ 

in tungstens eompounds (e. _ r .. WO d a hexad in 

tin u impound W i i altfl 

illed tui . and it ii 

•.. in Buch compounds thai thii element occurs in 
mineral Bcheelite lb a calcium tui 

fram i.» -•• ami iron ti. 

• f lead and oopp 

r. [\ m L r «»l«h ha peoifio 

- 1. 



278 DESCRIPTIVE CHEMISTRY. 

456. Uranium, IT, was discovered by Klaproth, in 
1789. It occurs in nature as an oxide, carbonate, and 
phosphate. The metal is malleable, is very slightly acted 
on by air at common temperatures, and has a silvery-gray 
color. It is a tetrad in uranous oxide (IT0 2 ), and a hexad 
in uranic oxide (IT0 3 ). Sodium uranate, known as uranium- 
yellow, is used foi coloring glass for optical and electrical 
purposes. Its specific gravity is nearly as high as that of 
tungsten, being 18*4, and its atomic weight is 238*5. 



CHAPTER XXV. 
GROUP 10. — TIN group: tin, titanium, zirconium, 

THORIUM, GERMANIUM. 

457. The metals of this group are quadrivalent ; tin 
and titanium also bivalent. In several respects they re- 
semble silicon, as in forming volatile compounds with 
chlorine (e. g., SnCl 4 ). 

Tin. 

Symbol, Sn. (Stannum) ; Atomic Weight, 118 ; Quantivalence, II and IV ; 
Specific Gravity, 1'S. 

458. History and Occurrence. — It is doubtful when tin 
first came into use, but it has been known probably for 
two thousand years. The alchemists gave it the symbol 
of Jupiter ( % ). It is seldom found native, but occurs 
combined in several minerals, nearly all the tin of com- 
merce being extracted from the oxide "cassiterite." The 
chief tin-mines of the world are in the Cornwall district 
in England, and the East India island Banca. Its ore has 
not been found in paying quantities in the United States. 
It is less common, and hence more costly, than copper. 



TIV 

459. Properties and Uses.— Tin is a brilliant silver- 
white metal, harder than lead but softer than gold or line. 
It is only dightly ductile, but ifl very malleable, and may 
be I into leaves /, of a millimeter thick It has 

little elasticity. The peculiar creaking sound given by 
tin when bent, called the u tin-cry," ifl due toadisturb- 
itruoture. Tin ia nol qnite aa heavy 
as iron, and has a lower melting-poini than any other 

Lmon n I Sulphuric and hydrochloric 

• upon it mi Qg, and nitric acid not 

unless dibit- - bul dightlyon exposure to the 

. and is therefore very valuable for coating 
otli ic«-t them fr<»m oxidising, though it u 

too soft and rtly to use alone for mosl purposi 

"Tin-] [ which so-called tin-ware is made, ifl 

Ouch has been dipped in melted tin. Copper 

nth tin in the same way. u Block-tin w ifl 
heavih inch lias been hammered to 

cause a i mion of the two metals. A cheap grade of 

tin-plate, .ailed ** n-rne-plat, ■/' ifl coated with an allo\ 

lead and tin. It- color is slightly bluish. It Bhould not 
be used for cooking-utensilfl nor tor canning foods, as 
there \g danger of poisoning from the lead. The tin-foil 

Used for ordinary purposed i> mad.- by rolline; out a sin 

of i ted with tin. Pini are made of bra— wire, and 

tinned I _ n water containing granulated tin, 

salt, alum, B iuble compound 

tin i- formed, and the liquid being acid, galranic action 

ni- 
.-. Tii vt of nil 

"ill alloy. / llov which COH- 

sbt~ tin to i | ntimonj . 

'•s a litt put in. /'■ 

4 parts of tin to 1 pa ometimes other ] 

erlj much used for ipoo 



280 DESCRIPTIVE CHEMISTRY. 

seded by German silver. Solder may consist of 2 parts 
tin to 1, 2 or 4 parts lead. Bronze consists of copper and 
tin, sometimes with a little zinc and lead ; bell-metal is a 
bronze of 4 to 6 parts copper to 1 of tin ; gun-metal is -^ 
copper ; our cents are made from a bronze consisting of 95 
per cent copper and 5 per cent tin and zinc. An amalgam 
of tin is used somewhat for silvering mirrors. 

460. Stannic Oxide, Sn0 2 (Binoxide of Tin).— This 
compound forms the heavy mineral, " cassiterite " or " tin- 
stone," which crystallizes in broad, flat prisms, usually col- 
ored brown or black by oxides of iron and manganese. 
Prepared in the laboratory it is a white solid, turning 
yellowish brown on heating. It is insoluble in water, or 
in acids except sulphuric acid. It acts both as a basic and 
an acidic oxide. Stannic oxide is used to make enamels 
and glass opaque ; also, on account of its hardness, to make 
a coating for razor-strops. 

461. Stannous Chloride, SnCl 2 (" Tin Salt").— This is 
a white crystalline solid, which melts at 250° C. It has a 
strong attraction for both oxygen and chlorine, and hence 
is used as a reducing agent for many purposes. It is also 
employed in dyeing. If a piece of zinc is hung in a solu- 
tion of stannous chloride, made by dissolving tin in hydro- 
chloric acid, the tin will be deposited on the zinc in a 
spongy mass called the " tin-tree." 

462. Stannic Chloride, SnCl 4 (" Butter of Tin "), may 
be made by passing chlorine over melted tin. It is a thin, 
colorless, fuming liquid, which boils at 115° C. When a 
little water is added, it turns to a pasty mass, called " but- 
ter of tin." It is much used in dyeing to fix and brighten 
red colors. 

Stannic Sulphide, SnS 2 , is a yellow substance, used, 
under the names " mosaic gold " and " bronze powder," 
for coating various articles in imitation of gold or bronze. 

463. Titanium, Ti, was discovered by Gregor, in 1791. 
It is a dark-green, rather light metal (sp. gr. 5*3), with an 



BI8M1 in QB01 iv 2S1 

IS. It forms titanous compounds, in 
which it is a dyad, and titanic compounds, in which it \& g 
tetrad Titan , or anhydride (TiO t ), occurs in na- 

ture 88 the mineral rntile, which often appears as hrown 
a in quartz. It is a white solid, which turns black 
when Btronglj heated, and is insoluble except in hydro- 
iling Bulphuric acids. Titanium is remark- 
affinity for nitrogen, forming several 

nitrides, and a eyano-nit ride (Ti X ON). 

464. Zirconium, Xr, OCCUra in certain rare minerals 
as an oxide and a silicate. It resembles silicon, occurring 
in three allotropic states. Its atomic weigh! is 90, and 

;*\ 1*15. It has never been melted. Zir- 
i tetrad forming only one oxide (ZrO f ), riroonia. 

465. Thorium, Th, discoyered by Berzelius, in l 

is of a gray color, and has a specific gravity ot r*. It is 
it, forming one oxide (ThO f ), thoria. atomic 
• 1. 

466. Germanium, (ie, was discovered in 1886, by 
ikler, in a silver-ore ot Freiberg, in Saxony. It is one 

of • ce tras predicted from tin- 

gaps in the Periodic Table. It has a grayish color and a 
Its specific gravity is 5*5, atomic ireighl 72, 
- as a dyad and tetrad. 



OHAPTEB \\\I 

1 1. — hi-mi I II OBOl P : BI8M1 l ll. \ \ s \ I'M K, 

N 10BI1 M. I \ N I \ I.I M. 

467. Thbsi elements, bj qnantivalenoe and • <• 
chemical pro] i u ith the I 

I »n the other hand. : d by 

tallic oh 



282 DESCRIPTIVE CHEMISTRY. 

Bismuth. 

Symbol, Bi. Atomic Weight, 208*2 ; Quantivalence, III and Y ; Specific 

Gravity, 9*8. 

468. Properties. — This metal, which has long been 
known, is found, in the metallic state, in veins in gneiss, 
clay, slate, and other crystalline rocks, chiefly in Saxony 
and Bohemia, and less commonly in combination. The 
commercial supply is derived from the native metal by 
purification. It is hard, brittle, reddish-white in color, 
and crystallizes from fusion in rhombohedrons. It melts 
at 264° C, and on solidifying expands one thirty-second of 
its bulk. It is volatile at high temperatures. Heated in 
the air it burns with a bluish flame, giving rise to yellow 
fumes of oxide. Bismuth is used in alloys to make them 
melt easily, and its compounds are employed in medicine. 

Various " fusible metals," consisting of bismuth, lead, 
and tin, are manufactured, which melt below the tempera- 
ture of boiling water. One use of them is for safety- 
plugs in steam-boilers. When the plug has become heated 
up to its melting-point, it gives way and lets the steam 
escape. On account of its great expansion in solidifying, 
bismuth is added to type-metal when small sorts are to be 
cast, and a sharp impression is hard to get. 

469. Compounds. — This metal forms a bismuthous 
oxide (BiO), and a bismuthic oxide (Bi 2 3 ) ; also a bis- 
muthic anhydride (Bi 2 5 ), and the corresponding acid 
(HBi0 3 ), metabismuthic acid. The neutral salts of bis- 
muth, by the addition of water, are decomposed into basic 
salts and free acid, thus : 

BiCl 3 + H 2 = BiOCl + 2HC1. 

The basic salt separates as a white precipitate. As this 
property is shared only by antimony, it may be used in 
analysis to detect the presence of bismuth. 

470. Vanadium, V, was first discovered by Del Rio, in 



>ld GRorr. 

1801. I train minerals with lead, iron, and oop] 

. and has - [te 

L*3, and its quantnralence i- III and V, 

It :" s. Vanadic acid ( II a Y< > 4 ) -Its, 

1 vanadates, isomorphoua with phosphal 

471. Niobium. weight .'Land Tantalum, 

rare nirtals, occurring 

top- - and tantalatea in certain minerals. 

Ill and V. 



I EAFTBB XXVII 

8R0UP 12.— OOLD GROUP : GOLD, PLATINUM, PALLADIUM. 

RHODIUM, IIIIKHM. KITIIKMIM, AM> 0BMITOC. 

472. N known b mmon to 

all: re of this irr< »u]». They are no1 alike in quan- 

; and triad, while the platinum 

talfl hav( ( told and platinom do not 

combin- lv with ; palladium, rhodium, and 

iridium when heated, but the oxides are broken up 

mm and osmium form volatile 
. which are nol decomposed by heat The 
lat* ted to the iron 

form comp 

ether sa * % noble 

•iat 

deluded in the 

Symbol, A u. (A urum). JeDOt, I and 

III; Specific G 1Mb 

473 Gold was ki ths 

alci O), 



284 DESCRIPTIVE CHEMISTRY. 

and their chief object was to produce a substance, called 
the Philosopher's Stone, whose touch should transmute 
the base metals into gold. 

This is one of the most widely diffused of the metals, 
and generally occurs in minute grains, diffused through 
quartz, galena, iron pyrites, and other minerals, though 
sometimes in masses weighing many pounds. The " Wel- 
come Nugget," found in Victoria, weighed nearly 183 
pounds, and yielded metal worth over $40,000. Consid- 
erable gold is found along the beds of streams, in gravel 
formed from gold-bearing rocks. It 
sometimes occurs in crystalline form, as 
shown in Fig. 147. Gold is always 
found in the metallic state, but rarely 
pure, being generally mixed with a vari- 
able quantity of silver. It is separated 
from all the constituents of its ores ex- 
cept silver, by amalgamation with mer- 
fig. 147.— Crystal of cury, and is freed from silver by boiling 
the amalgam in nitric acid, which dis- 
solves out the silver, leaving the gold pure. In this oper- 
ation, in order to prevent the silver from being mechan- 
ically protected from the action of the acid, it is necessary 
that there should be three times as much silver as gold. 
As the gold constitutes only one quarter of the mass, the 
process is known as quartation. 

474. Properties. — Gold is the only metal of a distinct 
yellow color, it has a brilliant luster, and is very heavy. 
It is the most malleable of the metals, and to its ductility 
there is scarcely a limit ; when pure it is nearly as soft as 
lead. It fuses at about 1,240° C, and shrinks when it so- 
lidifies. It is not acted on by sulphureted hydrogen, and 
does not oxidize in the air at any temperature. Gold is 
not dissolved by any single acid except selenic, but is acted 
upon by chlorine, or any solution which liberates that gas. 
Its usual solvent is a mixture of four parts of hydrochloric 




GOLD 

- nitric acid, which convert it to a ahloride, and 
ailed, on a power to dissolve 

rey< ). It ia oi i the besl oonducton 

heal andel( li forms a white amalgam with mer- 

cury. Verj thin lt « » 1 « 1 - 1 * ; 1 1* ia transparenl to green light 

aten oul bo as to cover L89 
b, and a pile I nly an inch 

high. (Jold wire can be drawn ao fine that ^/Mt> met 

475. Uses, (hi account of its rnnaininLr imtarin.-ln'.I 

the gases oi the atmosphere, and nnoorroded by oon- 

Ltfa all ordinary substances, <rold lias always heen 

metal for articles of ornament This durable 

ther with its scarcity, caused it- early adop- 

rm of money. The pure metal issosofl thai 

articles mad on irear out, hence it is almost 

Hritfa silver or copper, or both, according 

>r Lb wanted For jewelry, 
the proportion of gold in the alloy i> expressed in 
the word meaning -imply twenty-fourths, and no lit, 

as wln-n ap] jewelry ia made thai is 

English standard gold 
Cor coinage is twenty-two carats fine. The coinage Ian 
requires thai gold coins shall 
the alloys, nine part- silver to i copper 

used, in to imitate the color of pure erold. \ 

great deal of gold is used in the form of foil (gold-l< 
for filling I .1 for lettering and for gilding 6rna- 

. and build- 
ed in electro-platii tnd 

the double i 
•Id and potassium I Ad- 

hoe le from ire. 

ther use of gold Aoringglaas a ruby-n 

476. Compounds. Gold bai little affinil ther 
element*, and all it.- compounds are reduced bj ( in 



286 DESCRIPTIVE CHEMISTRY. 

the open air. Auric chloride (Au01 3 ) is a red, crystal- 
line, deliquescent solid, soluble in water, alcohol, and 
ether. By contact with the skin and other organic sub- 
stances it is reduced, depositing a purple stain of finely 
divided gold. Hence its use in photography (416). A 
complex substance is obtained as a purple precipitate by 
adding a mixed solution of stannous and stannic chlo- 
rides to a solution of auric chloride. It is called " the 
purple of Oassius," and is the substance used in coloring 
glass red. By heating to 175° C, auric chloride is con- 
verted to aurous chloride (AuCl). A double sulphide of 
gold and potassium is used for gilding china. 

The presence of gold in solution is detected by adding 
ferrous sulphate or oxalic acid. Metallic gold is precipi- 
tated as a brown powder, which takes on a metallic luster 
when rubbed with a hard body. 

§ 2. Platinum. 

Symbol, Pt. Atomic Weight, 197*4 ; Quantivalence, II and IV ; Spe- 
cific Gravity, 21*5. 

477. Platinum was discovered by Wood, of Jamaica, 
in 1741. This valuable metal is always found native, and 
usually associated with palladium, rhodium, and iridium. 
It also occurs alloyed with gold, copper, iron, and lead. 
Its chief sources are the mines of the Ural Mountains, 
Mexico, and Brazil. Platinum is a hard metal, of a gray- 
ish-white color, and closely resembles silver in appearance. 
It is one of the heaviest of metals, and when pure it is 
scarcely less malleable than gold and silver ; is very duc- 
tile, and takes a good polish. But the qualities which ren- 
der it so useful, and in some cases indispensable to the 
chemist, are its extreme infusibility (being unaffected by 
any furnace heat), and the perfect manner with which it 
resists the action of almost all acids. It does not oxidize 
in the air at any temperature, and is not acted upon by 
simple acids. Being strongly electro-negative, it is used 



i UK n.AiiM m mktals. 887 

in the pilvanic battery It is slowly dissolved by aqufi 
regia, and is corroded by beating with caustic alkalies, alka- 
line eyanid. »n, phosphorus, silicon, eta A Few pei 
iridium inc the durability of platinum, and 

i an a!. ihemical apparatus, We have 

ady allu power p 

and causini: the union of 

\~Mack i> a preparation 
d in a still more minute state of subdivision, 

a the property ol effecting chemical changes more 
tically than platinum sponge. It may be produoed 

g a dilute Bolution of the metal. 

478. Platinic Chloride, PtCl* is obtained by dissolving 
platinum in aqua regia and evaporating the solution over 
the i brownish-red substance, soluble in 
water and alcohol, forming a reddish-yellow solution. It 
is a valuable reagent for the determination of potassium 

ith which it form- double ohlori 
JKC1), slightly soluble in water, and there! 
separating a,s yellow crystalline precipital 

479. Iridium, Ir, * -d by Tennant, in It 

It was bo naned from the varied colore compounds 

, rainbow), to atomic weight is 198, speeiti< 

gravity 1 and tetrad. On 

accouir nesfl it is used for the ti] 

480. Osmium, Os, was discovered in the same 
with iridium, by I In the crystalline 
stat- ,d is th( 

481. Palladium, Pd, L06-5, Rhodium, Eth, 104, and 
Ruthenium, Ru, I hard white metali found in 

platinum. Palladium is liL r i<' 
in platinum, is mal ind du< I I the m 

inum metalfl. It I 
pedal 1;. v times its 

• <»f hydrogen. Its alloy wit! ii used 6 



288 



DESCRIPTIVE CHEMISTRY. 



weights. Rhodium is less fusible and ductile than plati- 
num. Ruthenium is brittle, and extremely difficult to 
fuse. It was discovered by Claus, in 1846 ; palladium and 
rhodium by Wollaston, in 1803. 

482. Groups of the Metals. — For convenience the 
twelve groups under which the metals have been studied 
are here given : 



1. Metals of the Alka- 


Silver. 


Tungsten. 


lies. 


Mercury. 


Uranium. 


Lithium. 






Sodium. 


6. Cerium Group. 


10. Tin Group. 


Potassium. 


Yttrium. 


Titanium. 


Rubidium. 


Lanthanum. 


Germanium. 


Caesium. 


Cerium. 


Zirconium. 




Didymium. 


Tin. 


2. Metals of the Alka- 


Erbium. 


Thorium. 


line Eartlis. 






Calcium. 


7. Aluminum Group. 


11. Bismuth Group. 


Strontium. 


Aluminum. 


Vanadium. 


Barium. 


Gallium. 


Niobium. 


3. Magnesium Group. 


Indium. 


Tantalum. 


Beryllium. 




Bismuth. 


Magnesium. 
Zinc. 


8, Iron Group. 
Manganese. 


12. Gold Group. 


Tron 


Ruthenium. 


Cadmium. 


Nickel. 


Rhodium. 


4' Lead Group. 


Cobalt. 


Palladium. 


Thallium. 




Osmium. 


Lead. 


9. Chromium Group. 


Iridium. 


5. Copper Group. 


Chromium. 


Platinum. 


Copper. 


Molybdenum. 


Gold. 



CARBON I OMPOUNDS 



DIVISION III. — I hi: carbon compounds. 



483. Character of these Substances.— Tin- simple com- 
pounds <»f . corresponding to those which other 

d-metallic elements form, have already been described 
Bui carbon forms other compounds which 
are so num< rhicb illustrate such interesting chem- 

J princi] ; which include bo many useful sub- 

stances, that they are regularly studied by themselves. It 
was formerly believed that these compounds could be pro- 
ed onlv by the "vital force n in a vegetable or animal 
ivisiou of the science was known as 
i hemistry." Among the most striking charao- 
- of these Bubsta the small number of cle- 

ats which enter into them, the hulk of all organi 
icturee being made up of the four elements carbon, 
and nitrogen. Carbon compounds are 
also remarkable for the great number of in the 

lea of many of them— forty-five in the sugar mole- 
vo hundred or more in her substau 

• arrang many atoms is often comp 

an : ich opportunity f«>r varied grouping, which 

.-.■ tn ii rism. The framework 

or I I hain of 

which may reach a gn _'th. In SOI 

be carbon chain 

01. 

484. Homologous Series I 

atom of it may unite with four ;> If 

together, one 1m.jp! «.f rm-h 
ng employed in ; them, they can take uj 



290 DESCRIPTIVE CHEMISTRY. 

six atoms of hydrogen, or two more than a single atom, 

thus: 

H H H 

i ii 

H-C-H H-O-C-H 
i ii 

H H H 

Methane. Ethane. 

The addition of another atom of carbon increases the ca- 
pacity of the chain to hold hydrogen by not more than 
two units. In this way a series of compounds is built up, 
each differing from the preceding by the common differ- 
ence CH 2 , and called a homologous series. Large groups 
of carbon compounds are related to each other in such se- 
ries, and, as the properties of the members of a series differ 
in a regular gradation, both the chemical character and 
the constitution of these substances are made easy to com- 
prehend and remember by this relationship. A general 
formula may be devised for any series, which shows the 
relative number of hydrogen and carbon atoms in the 
members of the series. Thus, the formula of the paraffins, 
to which methane and ethane belong, is C n H 2 n+2? where 
(n) stands for the index of C, and has different values in 
different compounds. The index of H is always two 
greater than twice that of C in the same paraffin. For in- 
stance, in ethane n=2 and the index of H is 2x2+2=6 ; 
in the member of this series containing seven atoms of car- 
bon the number of hydrogen-atoms will be 2x7+2=16; 
i.e., C 7 H 16 . The formula of another series, the defines, 
is OnHgn. 






291 



OHAPTBB WY11I. 

: Mi:in \ i;i\ vnvrs OB r \ in OBOl P 

HI DRO LRBOfi 

si.'/' 

485. Classification. Tin Bydrocarbonfl areth< 

3 which contain only carbon and hydrogen. T) 

>f them, some of u hich belong 
to w called tl roup, and the others to the 

'.mup. The Paraffins form the first series in 
the Fatty Group, and are so named on account of their 
reei- to chemical action (parti meaning 

lit t : l). 

486. Methane, c II. ( .1/ is firs! member 
• he paraffin » a colorless, inodoroc 

which burns with a scarcely luminous Bame. It may be 
liquefied under a pr . • — 1 1 J C. 





V V \ , 




m^ 






~ V 








" 


\ 


















M 












| 




148.-C 


olltclliig ]faf>h «;**. 





292 DESCRIPTIVE CHEMISTRY. 

If diluted with air, it may be breathed without harm. It 
is called marsh-gas because it is a product of the decom- 
position of vegetable matter under water in marshy places. 
It may be collected by inverting a jar and funnel in the 
water, and stirring the mud beneath (Fig. 148), when the 
gas rises in bubbles and enters the jar. It may be pre- 
pared artificially by heating together two parts of sodium 
acetate, two of potassium hydrate, and three of quick- 
lime: 

NaC 8 H 8 O t + KOH = NaKC0 3 4- CH 4 . 

Another method is by passing a mixture of sulphureted 
hydrogen and carbon disulphide vapor over red-hot copper 
turnings. 

Since this gas is produced from vegetable substances 
by substantially the same process which yielded our de- 
posits of coal, it is not surprising that marsh-gas is found 
in the crevices and cavities of coal-beds. Mixed with 
more than six times and less than fourteen times its bulk 
of air, it explodes violently, and constitutes the fatal 
"fire-damp " of coal - mines. Carbon dioxide (" choke- 
damp ") is formed by the combustion, so that the miners 
who are not killed by the shock or flame of the explosion 
are generally smothered by the latter gas. 

In some coal regions there are vast subterranean cav- 
erns filled with this gas under great pressure. Borings are 
made in the earth, through which the gas presses up and 
is used for lighting and heating purposes under the name 
of natural gas. Other more luminous gases are mixed 
with the methane in natural gas. The village of Fredo- 
nia, N. Y., has been lighted by this means since 1824. 
From about 1885 much use has been made of it in west- 
ern Pennsylvania, Ohio, and Indiana. It is used for 
lighting streets and buildings, for burning in stoves and 
grates, and in the furnaces of glass-works, iron-foundries, 
and other manufactories. 

487. Coal-Gas. — When coal is heated, gas is driven off, 



COAI. G kfl 

which, ou account of its srreat 1 i irli t inir and heating power, 
and thf convenience with which it can be conveyed and 
controlled, has come into wide use, making its manuiact- 

■:ie of the most important industries. Coal-gas is a 

mixture of hydrogen, methane, ethane, nitrogen, carbon 

and di< ral other gases present in 

■nailer quantitiea The bituminous coal aenring tor its 

me <>{ I instituents, while 

others an ted by decomposition ; hence the process 

itructive distillation. Methane is the chief 

tdtuent, making 50 or more per cent of its hulk, but 

only the presence of other hydrocarbons (benaene, defiant 

ga8,ete.)mak one luminous. The coal is heated in 

cylinders of cast-iron, and the gaseous products Conducted 
which always contains water through which 
. unroll ammonia and ammoniaoal salts. 
At the same time coal-tar is deposited in the tube, as a 
3cid thud. The removal of carbon dioxide and 
mlphureted hydrogen is effected by conducting the gas 
: ferrous sulphate, daked lime, and 
sawdust. After being purified the #as is collected <>ver 
* iron cylinders called gasometers, from which 
•d out through pipes to the places where it i- to 
be co: The coal in the retorts has beoome light 

as, and is ki i \ poison- 

ous, an 1 deaths are constantly occurring from its esoape 

ur of Bleepin^-rooms. It also en-apes from dr- 
ily managed fun ato the air of houses. 
tains a uriety of ingi . and 
has become an in. 4 chemical mani 

teal liquor which is 
also a so iseinl pr 

488 Higher Members of the Series. 

ratlin 

• lorless gas, bun itfa a 

faintly lumin< be liquefied mo 



294 DESCRIPTIVE CHEMISTRY. 

than methane, condensing under a pressure of 46 atmos- 
pheres. Propane (C 3 H 8 , or CH 3 .OH 2 .CH 3 ) is a colorless 
gas, which condenses to a liquid even more readily than 
ethane, a cold of —25° to —30° 0. being enough to liquefy 
it without artificial pressure. 

489. Isomeric Modifications. — Butane, C 4 H 10 , the next 
member of this group, exists in two modifications. Nor- 
mal butane is a gas, which may be liquefied somewhat be- 
low 0°. Isobutane is also a gas, liquefying at —17°. It 
is believed that these modifications depend upon a differ- 
ence of arrangement among the carbon-atoms in the 
molecule. It is impossible to link two or three atoms of 
carbon in more than one way, but four atoms of carbon 
may be united in two ways, thus : 

I I I I II! 

-0-0-0-0 - -C- C-0- 

i I I I III 

-0- 

I 

In one arrangement, no carbon-atom is joined directly to 
more than two other atoms of carbon ; in the other, one 
carbon-atom is joined to three others. A compound of 
the former type is called a normal, one of the latter type 
an iso, compound. A chain of five carbon atoms may be 
arranged in three ways, and three modifications of pen- 
tane (C 5 H 12 ) are actually known. The one whose graphic 

formula is ^tt 3 > C < nrr 3 is named tetra- methyl me- 
thane, because it may be regarded as a molecule of methane 
(CH 4 ) in which each of the four hydrogen-atoms has been 
replaced by a methyl radical (CH 3 ). Each addition of a 
carbon molecule to the chain makes a great increase of 
the number of possible isomers ; thus C 6 H U may be ar- 
ranged in five ways, C 10 H 2 2 in 75, and C 13 H 28 in 799. But 
few isomers of the higher members, however, are known. 

490. The Paraffins. — These substances, while having a 
general resemblance in character, show also a gradual 



THE PAK 






change of pi - as we asoend the Specific 

I the lmilin.LT-poim bus ■ the 

three ru re gases at common 

temperatures, then follow several which are liquid, while 
the Inched are BolicL 

Tin: Paraffins, General formula I . II . 



\ WW 




1 


1 




CH« 

C,H, 

1 Jl 
1 II,, 

1 1 

r.H , 

C I. 
Bt, 
B M 
! l . • 

1 B M 
B 
Bn 


1 
38 
W) 
M 

l-i 

i-i 


.... 










r ■ • . . 


218 




. . 



In le the boiling-points and 

►rmal paraffins are given. Various ele- 

ind rad I {<>v pari or ;»11 <>f 

llv bromine, form 
tly in sunlight, while iodidt 
be formed indirectly. v i does not ad on I 

par.. i form • inds, as OB Si I . the 

liquid, 

nr i IvchI in . im, whi< >f ;i 

mixture of liquid parafl 
also found dissolved n 

I 
tlen .-ill produced h 



296 



DESCRIPTIVE CHEMISTRY. 



matter, which were covered with earthy material by some 
upheaval of the earth's crust, and then heated from inter- 
nal sources. In this way a destructive distillation was 
performed on an enormous scale. 

491. Fractional Distillation. — In treating organic sub- 
stances, it is frequently necessary to separate liquids hav- 
ing different boiling-points from a mixture. This is most 
conveniently done by fractional distillation. The mixture 
is poured into a flask provided with a thermometer, and 




Fig. 149.— Apparatus for Fractional Distillation. 

boiled. The vapor given off passes through a condenser 
consisting of a glass tube around which cold water is kept 
flowing in a tin jacket, and is condensed to a liquid. The 
temperature in the boiling-flask gradually rises as the boil- 
ing proceeds, and the distillate which passes over while 
the mercury is rising through each five or ten degrees is 
collected in a flask by itself. After the mixture has all 
been distilled, the first of these fractional products is re- 
distilled. It will not all go over between the same degrees 
as before, so to what is left in the boiling-flask when its 
upper limit is reached the second fraction is added, and 



PETROLEUM. gpf 

inued, the distillate being oollected in 
the Ban - of flasks i If two Ii(jui 

I whose boiling-points are, for instai 
it will be found that the fractions in- 
cluding tin tvcs will grow larger with each distil- 
ion and the others smaller, till two portions are ob- 
tained comprising all of the liquid, and boiling at th< 
tits. 
492. Petroleum. -( Latin , itm, rook-oil.) This 
is a combustible liquid, which issues from the ground in 
-, and was mentioned by the Greek and 
tin writ. : little use was made of it until the 
ing wells was begun in western Pennsylva- 
.. in 1859, which gave a plentiful supply. Other im- 
portant localities are the vicinity of Baku, on the Caspian 
Sea, and t: . district in Burmah. Petroleums 
from different pla lifferenl degrees <>f fluidity, 
riously colored, the Ajnerican <>il haying a 
dirt All have a d ible odor. Though 

3 of oth( . petroleum 

mainly a mixl paraffins. In American petroleum 

■8 of the BerieS prevail; the Russian 

utains the higher members to a considerable 
L Their complete separation requires various chem- 

mipulations, but by a simpler process they may he 
sep:: nd purifi ■ furnish an oil lit for 

illnmii. In refining the crude oil, u n 

sirn' ire at firel removed by i 

•it with sulphuric acid, sodium ! It 

i distill I tot, distill- 

en certain 1 

tfer 

onions by too volatile admix 1 



298 DESCRIPTIVE CHEMISTRY. 

of this country an oil is rejected if taking fire at less than 
38° C. (100 F°.). 

493. Testing Kerosene. — Various forms of apparatus 
have been devised for determining the flashing-point. Ee- 
sults depend partly on their construction, and partly on 

the experience and dexterity of the 
operator. The simple apparatus, 
represented in Fig. 150, is recom- 
mended by Prof. Eemsen, in his 
" Organic Chemistry." The cylin- 
der a, 2 cm. in diameter and 10 cm. 
long, is closed at its lower end by a 
wooden plug ; the glass tube c, pass- 
ing through it, is at its end con- 
tracted to a small orifice, b. At d 
^c it is connected with a hand-bellows, 

Fig. 150. -Kerosene-Tester, or other source of compressed air, 
the flow of which can be controlled 
by a pinch-cock. The cylinder a is secured in a clamp, and 
about one third filled with kerosene. It is then immersed 
in a water-bath to the level of the oil. Air is then passed 
through d, c, £, while e is so adjusted that about 0*5 cm. of 
foam is formed on the surface of the oil. As the tempera- 
ture shown by the thermometer / rises, from time to time 
a small flame is brought to the mouth of a. When the 
flashing-point is reached, the vapor ignites, and a blue 
flame is seen running down to the surface of the oil. 

494. Other Petroleum Products. — The substances in 
petroleum of lower and those of higher boiling-point than 
kerosene also have their uses. The most volatile product, 
boiling at about 18° C, is called rhigolene. It evaporates 
so rapidly at common temperatures as to produce great 
cold, and has been used to dull sensation in parts of the 
body for surgical operations. Gasolene boils at about 
49° C. The gas-machines used to supply gas to single 
buildings furnish a mixture of air and gasolene-vapor. 



nmoLHUi room i 

ral grade- tiling-points bei 

gasolene and kerosene, are used for dissolving 
resin- ad rubber, and for burning in specially 

gtructetl lamps and other commercial names 

these 1:. , Ligroin, and p 

leum-spirit. U boils at a higher bempera- 

bhan k< md will nol take fire beloi L60 I 

■d for lighting on b . •• here 

il is required. The ating 

ill higher temperatures. Ahove these stands 
the | known commercially bb par L 

ial petroleum products H is a mixture 
of h\ high boiling and 

e paratline is a .-"lid a! eommon tem- 

I ... and odorless sub- 

stane- ailiar ose is m candles, lmt its power 

of r« b chemical action adapts il to many other im« 

i employed for preserving meat, fruits, 

and timfa - fA acid-bottles, \'<>v insulating 

ating pills, tor making matches and 

1 for many other purposes. 

of burning L r .-i- s hich has lately 
To maki m is led over red-hoi an- 

thracite coal, by irhich it is decomposed, thus ■ 

E.0 f-C = CO • II.. 

trbon monoxide oor hydrogen yields muoh light 
in burning; hei the mixture <>f tli<-- lm-- 

suitable for illun tased through a hoi 

introduced. The higher hydro- 
gen up by the hi bane, 
p gases, and the resulting mixture is a gas 
though as a fuel- 
gas. On account <»f mon- 

amon 



300 



DESCRIPTIVE CHEMISTRY. 



§ 2. Other Series of the Fatty Group. 

495. The Olefine Series.— The typical formula of this 
series is C n H 2n ; each member having two atoms of hydro- 
gen less than the corresponding paraffin. There are sev- 
eral ways of explaining how such molecules are possible, 
the most probable one being that two of the carbon-atoms 
are united by two bonds, thus : 



H N 



,H 



H 



= 

Ethylene. 



H H 
I I 
= 0-0-H 
W ' 

H 

Propylene. 



Two atoms of a halogen or one of oxygen may be added 
directly to an olefine, forming what is called an additive 
compound — e. g., ethylene dichloride (C 2 H 4 C1 2 ). The two 
bonds of the addition are supposed to join with two of the 
bonds previously united in the double linkage. Olefines 
may be converted to paraffins by the addition of hydrogen. 
496. Ethylene, C 2 H 4 ( Olefiant Gas) is the best known 
member of this series. It is generally prepared by distill- 




Fig. 151.— Making Olefiant Gas. 



Tin: Arm i. km: skkiks ;:i ,1 

ight ol common aloohol with sb pa 
sulphuric acid at about 170 c. It i> a colorless L r a > of 
■ong odor, burning with a bright Same. 
-n mixed with air, it is explosive; it derives its name, 

_as," from tin* oik compound which it form! 

:i chlorine (( .II. < .). Ethylene is also produoed when 
wood and similar organic substanees arc subjected to heat, 
and it forms about - oal-gas. 

The defines up to ben atoms of carbon have been ob- 
Their nam.- correspond to those <>f the paraffins, 
II) and diamylene 1 1 ; 11. ). Th 

known also triam\ I I « . II,,), tc 

. and melissene (< ,„H M ). 

The lower i: re erases, the higher arc 

liquids. 
497. The Acetylene Series.— The general formula of 
this ser Tile molecule of each member is 

tain a j»air of carbon-atoms that are joined 

three bonds, e. g., B-C II (Acetylene). But 

ra of th( known, of these the low 

are gases and the others liqu 

I \ [„ froin which the series tak uue, 

is a gas of a penetrating smell, burning with a lumiin 
smoky flam- -ial interest as a hydrocarbon 

which can be obtained by the direct onion <>f its elements, 

ing forn . the current from a powerful ban- 

passes, in an atmosphere <»f hydrogen, between carbon- 
les. It is also the product «-f decomposition by heat or 

im; ion of organic compounds, DK) 

tly by burning coal-gas with an insufficient supply 
or. 

498 Halogen Derivatives. Among the nun om« 

Isresultu j I halogens upon hydro- 

car their d< hare the most 
pra 



302 DESCRIPTIVE CHEMISTRY. 

long known by the name of Dutch liquid (C 2 H 4 C1 2 ), is 
obtained by direct union of equal volumes of chlorine and 
ethylene gases, and is a colorless, heavy liquid of fragrant 
odor and sweet taste. Chloroform, or Trichlormethane, 
CHC1 3 , a colorless liquid of 1*52 specific gravity and boil- 
ing at 62° C, of pleasant odor and sweet taste. It is pre- 
pared in different ways, most commonly by distilling alco- 
hol with commercial chloride of lime (bleaching-powder). 
In this process, trichloraldehyde (chloral) is first produced, 
which is then converted by the calcium hydrate, always 
present in chloride of lime, into chloroform, as follows : 

2C 2 HC1 3 + Ca0 2 H 2 = 2CHC1 3 + CaC 2 H 2 4 

Chloral. Calcium Chloroform. Calcium 

hydrate. formate. 

The vapor of chloroform when breathed renders a person 
insensible, hence it is largely used to make patients un- 
conscious of pain when surgical operations are to be per- 
formed. There is a similar bromine compound called 
bromoform. Iodoform, CHI 3 , is obtained by treating an 
alcoholic solution of iodine with potassium hydrate ; it is 
a yellow, crystalline powder of a strong, saffron-like smell, 
and has been for years considered as a valuable antiseptic 
in surgery. 

499. Cyano-paraffins. — Supposing that in methane three 
atoms of hydrogen are substituted by one atom of triva- 
lent nitrogen, the compound CNH resulting for CH 4 , we 
observe that we have arrived at the formula of hydro- 
cyanic acid. Cyanides, therefore, in which the hydrogen 
of this acid is replaced by some other element, or. radical, 
and all the cyanogen compounds together may be consid- 
ered as methane derivatives. One of them is Fulminic 
Acid, not known in the free state, but in combination with 
mercury giving a salt, which, on account of its strong ex- 
plosive properties, is used for filling percussion-caps. The 
formula for fulminic acid is assumed to be CN.CH 2 N0 2 , 
that of its mercury salt CN".CHgN0 2 . 



ALoonoia 

500. Alcohols. — If in a paraffin one hydro mil 

substituted by hydroxyl, the univalent radical <>H, an 

methane becomes methyl alcohol, 

'Hi. ethane becomes ethyl aloohol (('. II nil). The 

radicals, methyl (CH,), ethyl ir.H.i. etc., have not k> 

lated,but in many substitution products the] are known 

. t<» tin- character <>f metala Bj comparing 

some ethyl compounds with tl sodium, the similar- 

stitution becomes apparent : 

oil Ethyl hydroxide, \ <>ll Sodium 

or AlcohoL hydroxide. 

( EL] n Ethyl oxide, or , 

0. *• I I - .iium oxule. 

Ether. 

Ethyl nitrate. \a\< > Sodium ail 

ohol radicals may take more than one hydroxy! radi- 
. forming polyhydric alcohols. Any or all of these hy- 

for other radicals. The follow- 
mpounde represent the different sorts of polyhydric 
known : 

Qohydric, C H,(OH) Ethyl aloohoL 

Dihydi I H : «<>Ih, GlyooL 

ihydrio, I B (OB >-< Glycerin, 

trahydric, I ,B (OH)< Erythrit 

a ihydrio, I ".II.mHI >. Ifannite. 

501. Methyl Alcohol OH OH MI This is 

chief products of the dry distillation of wrood. 
i thin, colorless liquid, rery similar in 
mmon aloohoL < Jrude wood-sp 

always inn . •• odor, 

: r<»r 

•f the purposes for whirji onlin 

especially in the manuf 1 famishes. I? ned 

as a burning material in lain 

502 Ethyl Alcohol. I 1 1 ff (< 



304 DESCRIPTIVE CHEMISTRY. 

its of Wine). — When solutions of sugar, or the saccharine 
juices of plants, are acted upon by ferments, they are de- 
composed, with evolution of carbon dioxide, and formation 
of alcohol : 

C 6 H 12 6 = 2C 2 H 6 + 2C0 2 

Grape-sugar. Alcohol. Carbon dioxide. 

This alcohol may also be obtained from ethylene ; ethy- 
lene may be prepared from acetylene, and the latter may 
be formed by direct union of carbon and hydrogen ; thus 
it will be seen that it is possible by a series of simple re- 
actions to build up alcohol from its elements. It is a 
colorless, mobile fluid, of 0*79 specific gravity, having a 
pleasant, fruity smell and a burning taste. It is very vola- 
tile, and has a strong tendency to absorb moisture from 
the air or from bodies immersed in it, thus rendering it 
valuable as an antiseptic. It is highly combustible, burning 
with a pale-blue flame, and producing intense heat without 
smoke ; it is therefore well adapted to burn in lamps for 
chemical use. Alcohol has great value as a solvent, as it 
acts upon many substances which water does not dissolve, 
and is easily separated from them on account of its extreme 
volatility. It boils at 78-4 C., and does not freeze until 
cooled to —131° C, when it is converted into a solid white 
mass. In a concentrated form it is a potent poison, but, 
when sufficiently diluted, it acts upon the animal system 
as a stimulant. Taken freely in this form it produces 
intoxication, and is the active principle of all fermented 
and distilled liquors. 

503. Fermented Liquors. — Wines are obtained from 
the juice of the grape and other fruits. The fresh grape- 
juice, or musty is placed in vats in cellars, where it fer- 
ments, the temperature being so low that the process goes 
on very slowly. Sometimes the wines are bottled before 
the fermentation is quite complete, and they continue to 
generate carbon dioxide, which remains compressed within 
the liquid. If the gas is so abundant as to produce effer- 



ALCOHOLIC LlgCOKS 

vescrmv when uncorked, the wine is said to I /•/•- 

ling"\ if not, it is termed u still" wine. Clarei ind 

mtain from 6 to LO per cent of alcohol! 

unpagne about LO per cent, port and sherry Erom L6 to 

• nt. 

r Lb made from barley which baa been caused to 
•ut by the action of heal and moisture. The Bprouted 
in is called matt, and contains sugar, which is formed 

from thr standi in >«vd> wlum tlmv sprout. Soaking the 

t in wal liquid called the wort, and this 

is made to ferment by adding . thns yielding beer. 

I fr«nn nitrogeniaed products by a 

^•continued fermentation; hence it maybe 

without further decomposition. Before 

stored in vaults for months, from which 

t8 name is derived {lager, lair). It contains 
fro] ■ t of alcohoL The difference in color 

malt liquors ifl OWin.i: to tin- various drirrccs of Imat 

iployed in maltii is made from pale malt, while 

that usedfo is partly charred, giving it i brownish 

>r and bi i >r. 

504. Distilled Liquors are obtained by subjecting oer- 

distillation. Brandy is derived 
from tli. distillation of win< | from that of fermented 

molasses. Whisky is obtained from com, rye, and po- 
tatoes, by first converting their starch into sugar, then into 
irit, and distilling the product Qv\ ia produced by 

spirit from ;i mixture of barley and • 
1 owes its peculiar flavor to juniper-berries. Distilled 
liqu Icohol, but i 

Sold 

505. Higher Members of the Methyl-Alcohol Series 
Be*- vl alcohol, then r of al- 

Icnown I : to this 

I ! I '1 1 1. a solid obtained from !><•«•*- 
wax. I H I 1 1 1 i / 



306 DESCRIPTIVE CHEMISTRY. 

together with ordinary alcohol, in fermentation. It is a 
transparent, colorless liquid of offensive spirituous odor 
and burning taste, and is poisonous. It is to this alcohol 
that the injurious effects of spirituous liquors, for the 
greater part, must be ascribed. Some of its compound 
ethers are distinguished by a very fragrant odor, and there- 
fore are applied in making perfumery. 

506. Ethers may be regarded as the oxides of alcohol 
radicals, bearing the same relation to the alcohols that 
metallic oxides bear to the metallic hydrates (500). 

Ethyl Ether (C 2 H 5 ) 2 (Sulphuric Ether). —When 
equal weights of strong sulphuric acid and alcohol are 
heated in a retort, a vapor passes over which may be con- 
densed into a limpid fluid, called ether from its volatility. 
The name " sulphuric ether " is not correct, because it 
does not contain any sulphur. Ether is colorless, with a 
fragrant odor, a hot, pungent taste, and when inhaled pro- 
duces insensibility ; hence it is much used as an anaesthetic. 
It is so volatile that when placed upon the hand it pro- 
duces cold by rapid evaporation. It boils at 35° C, or when 
exposed to the air in hot weather, and is very combustible, 
burning with more light than alcohol, and some smoke. 
Its vapor, when mixed with air, is explosive. It readily 
dissolves fats and oils. 

507. Compound Ethers. — If ether may be regarded as 
the oxide of ethyl, then ethyl chloride, nitrate, acetate, 
etc., may be considered as salts of ethyl. They are com- 
monly called compound ethers, and are volatile liquids of 
a strong, rather pleasant odor. Ethyl nitrite (C 2 H 5 N0 2 ) 
is a compound ether. Its solution in alcohol is used in 
medicine under the name " sweet spirits of niter." Other 
compound ethers are the essences which give the different 
flavors to various fruits. 

508. Dihydric Alcohols. — The olefine hydrocarbons, 
by adding two hydroxyl radicals, form dihydric alcohols, or 
glycols , corresponding to the hydroxides of bivalent metals : 



OH Calcium n n IOH Ethylene 

[OB hydroxide. ' ' (> " glycol 

both of these hydxaxyls may be substituted by 
rH I OH Glycol | , ( I 01 Ethylene 

( ' chlnrhvdrin. * | 01 chloride. 

neutral, \ iscid liquids, having 
509. Trihydric Alcohols. 01$ , < H f (OH)„ ifl the 
only known trihydric alcohol The radical <',II 8 , united 

the basis of vegetable and animal hi 
it ifl ak .all amount formed in alcoholic fermenta- 

.. and t ; 9eni in wine and beer. Glycerin is 

- a by-product in the manufacture of soap and 
r. In theee prooooooo Cats, which must be re- 
garded as compound ethen oi leoompoi 

potash, soda, or had oxide, 
whi with the tatty acids, glycerin being 

Glycerin remains dis? in water, by the evapo- 

•f which it is obtained in a ooncentr 
en pun- it arly colorless, inodorous, rirupy 

liquid, of into « * 1 1 \ free from 

, forming a whil talline mass. 

ifl readily soluble in water and alcohol, and ifl I \;dual»lc 

• t. It is employed aa a medicine (<>v • 
interna] use ; and. on account of its k>1vh 

• admini 
I • employed in the menu- 

l 
tilled without uno bemical ehai 

1 
am 

6 whi<d, <ri- 

tat: 
fats when th 

510 Nitroglycerin, < II.i\<> tmixtun 



308 DESCRIPTIVE CHEMISTRY. 

strong sulphuric and nitric acids acts on glycerin at low 
temperatures, a violently explosive, oily liquid of light- 
yellow color is produced. This compound, more correctly 
called glycerin nitrate, has a specific gravity at 15° C. of 
1*6, is inodorous, but has a sweet, pungent, aromatic taste, 
and, placed upon the tongue, produces headache. Nitro- 
glycerin is exploded, not by the direct application of heat 
in open vessels, but when heated in closed vessels and by 
sudden concussion, and proper care in its preparation 
greatly lessens the danger attending its use. Nitrogly- 
cerin is the active constituent of a number of explosives 
applied for blasting rocks ; dynamite is infusorial earth 
impregnated with nitro-glycerin. 

511. Tetra- and Hexahydric Alcohols. — Erythrite, the 
only tetrahydric alcohol known, occurs as a compound 
ether in some sea- weeds and lichens. Hexahydric alcohols 
are represented by the three isomeric bodies, Mannite, 
Sorbite, and Dulcite, C 6 H 8 (OH) 6 , the first of which is a 
crystalline body of sweet taste contained in manna and 
many other vegetable products. The alcoholic character 
of mannite becomes evident by the fact that it may be 
artificially prepared from the aldehyde glucose by nascent 
hydrogen — 

C 6 H 12 6 + H 2 = C 6 H 14 6 , 

and that by oxidizing agents it is converted into a sugar 
of the glucose group (517). 

512. Amines. — There is a series of methane derivatives 
which may be considered as hydrocarbons, in which a 
hydrogen-atom is substituted by the univalent radical 
amidogen (NH 2 ). Thus ethane (C 2 H 6 ) gives the product 
C 2 H 5 NH 2 . These substances, called amines, may also be 
regarded as ammonia, in which one hydrogen-atom is re- 
placed by the radical of an alcohol, which in the mentioned 
instance is ethyl. Amines are therefore also called substi- 
tuted ammonias. By repeated treatments with methyl 
iodide, one, two, and three atoms of hydrogen in ammo- 



ai.m in i 309 

nia may be replaced by methyl, forming methyl amine, 

( 11 3 , di-methyl amine. \ll(< llj., and bri-methy] 

. \ CH i.. Amines have an alkaline reaction and 

ammonia can be volatilized n ithoal de- 

opposition, and form Baits with acids. Tri-methyl amine 

an in several plan' ituenl of bone-oil, 

.-tar, and herring-brine. 

513. Compounds of Alcohol Radicals with other Ele- 
ments. — Alcohol radicals combine not onlj with oitro- 

., but also with the other members of the Bame group 
of elements — phosphorus, arsenic, and antimony. Most 

these compounds, called phosphines, arsines, and >ii- 
bines, are of analog ostitution to tri-methyl amine. 

Methyl arsine has the formula Am OH )» Several metals, 

-h as sodium, sine, tin, and lead, also enter into combi- 
:i with organic radicals. 

514. Aldehydes.-— Alcohols, when subjected to theac- 

lizing substana J, onyerted into aldehy 

Convei -ion into aldehyde consists in the 

thdrawal msof hydrogen; hence the name, 

from a rutfum. By the addi- 

tion of one atom ildehydes become acids : 

Mecfav •• 1 aldehydi 

Rhyl alcr.) 

Propyl a] -• -n Propyl a n e " rr.i 

Butyl Alooboi ( ! 4 H f ( >H Butyl aM.-lml.-. ( \U J >. Batjlic Add, ( \Hj '•, 

■1 kmj\ 

I I .< HO), the best known 

ind <»f * • be produ lual 

trious ws Jcohol, or bj trans- 

mit! of alcohol and air throi ain 

When a tew di 

placed ; .r will mingle with the air. I 

I of platinum u Dp 

m of tl. 1 nn- 

gent odors D otT, and the 1 



310 



DESCRIPTIVE CHEMISTRY, 





Fig. 153— Flame- 
lees Lamp. 



is kept at a red heat by the continued oxidation. If the 
coil is suspended over the wick of an alcohol or ether 
lamp (Fig. 153), it will continue 
to glow for hours after the flame 
is extinguished, from the same 
cause. Acetic aldehyde is a 
highly volatile liquid, boiling 
at 21° C, and possessing a pun- 
gent, suffocating odor. Some 
of its properties may be well ob- 

Fig. 152.— Ox- -i-i • -i 

idation of served by a simple experiment. 
Dissolve a little potassium bi- 
chromate in water and add sulphuric acid, then add about 
thirty drops of alcohol. Aldehyde is generated, and is 
noticed by the odor of the mixture. At the same time the 
red color of the liquid is changed to green by the reduc- 
tion of chromic acid (Cr0 8 ) to chromic oxide (Cr 2 O s ). 
The oxygen given off by the acid combines with a part of 
the hydrogen of the alcohol. 

Aldehyde has a strong disposition to combine with 
oxygen, and is quickly converted into acetic acid by stand- 
ing exposed to the air. This liability to oxidation renders 
it an effective reducing agent. Metallic silver is precipi- 
tated by it from silver nitrate solutions. 

515. Trichlor-aldehyde, CCl 8 .CHO (Chloral).— By re- 
placing three atoms of hydrogen in the formula of alde- 
hyde by chlorine, the formula for a compound known as 
chloral is obtained. It is formed by the action of pure and 
dry chlorine gas on absolute alcohol, and distilling with 
sulphuric acid the solid white mass of chloral alcoholate 
thus obtained. It is a thin, colorless oil, which boils at 
about 94° C. It has a peculiar pungent odor, and excites 
a copious flow of tears. Its taste is greasy, and slightly 
astringent. The vapor acts powerfully upon the skin. 
Mixed with a small quantity of water it becomes heated 
and solidifies to a white crystalline mass, Chloral Hydrate 



uin dkatks :;i i 

BtO), which is rotable in water, volat ili/.es urad- 

nallv in the air, ami may be distilled without decomposi- 
tion, i ied in medicine, as a means of producing 

j». 

Unmistakable hots give evidence that the oarbohy- 

drai -I under the name of glu re con- 

densed or polymerised aldehydes. M< thyl aldehyde can he 

ificially converted into a suirar, which ha- received the 
name of f ormoee : 6( IM> = i.lM». The near relation 

the L r lu the other carbohydrates requires eub to 

e the WJ \t to the aldehyde-. 

516. Carbohydrates constitute the chief material of 
ich plant- are huilt up, and they (..cur organised as 

I a- in the crystallised and theamorpho They 

contain the dementi carbon, oxygen, and hydrogen, the 

latter two in the same proport ion as in water. I > \ their 

o they are distinguished into three groups, 

viz. : (iluc< - -. * 1 1 < » . v .. : ' ' ' . Am\ loses, 

Th rtion of the elements of water, it is Bl 

rom the firsl t«> the third group. 

517. Glucose Group. -The chief representative 

uown as<rra] 
r with , another member of the group, 

in nature, and occur- most ahundantly 
in ripe fruits and in honey. It i^ artiii.-ialU prepared by 
of dilufc h, ami cel- 

lulose. The -aim :»y the unorganj 

fen germinal ti. (.In.',,.,. 

is also l i in the animal di in 

I* produces ri^ht-ham 
d in polarized light, 

minute, indistind 
Kagonal plates, fr<»m alcohol in ol»l. Lesi 

_ r ar, it dissolves in a: dit 

of cold wat 



312 DESCRIPTIVE CHEMISTRY. 

laevulose and galactose is, that in contact with yeast — an 
organized ferment — they undergo fermentation, being split 
up into alcohol and carbon dioxide (531). All members 
of the group are distinguished by precipitating, metallic 
silver from solution of its salts containing ammonia, and 
red cuprous oxide from alkaline solutions of cupric salts. 
It is particularly by the latter reaction that the presence 
of glucose is ascertained in cane-sugar and in other com- 
mercial products, to which glucose is often added fraudu- 
lently, on account of its low price. 

The test is made in the following way : Dissolve a 
little cupric sulphate and Rochelle salt in distilled water, 
and add so much solution of caustic soda that the pre- 
cipitate separating at first is redissolved, and a clear, dark- 
blue solution obtained. Heat several cubic centimeters of 
it in a test-tube, add a few drops of the dissolved question- 
able substance, and heat again. If glucose is present, 
the color of the mixture will suddenly change, and a red 
precipitate of cuprous oxide appear. Rochelle salt is 
added to the copper solution to increase its stability. 
This liquid is called " Fehling's solution." 

518. Cane-Sugar, or Saccharose Group. — The formula 
CwHggOn of these sugars is explained by two glucose mol- 
ecules combining and a water-molecule separating : 

2C 6 H 12 6 — H 2 = C 12 H 22 O n . 

Cane-Sugar is contained in the juices of many plants ; 
it is chiefly produced from sugar-cane and the beet-root, 
sorghum-grass and the maple-tree also furnishing a lim- 
ited supply. The methods of obtaining it from cane and 
beet-root are about the same. The canes are crushed by 
passing them between grooved iron cylinders. The juice, 
when first expressed, is liable to rapid decomposition from 
the heat of the climate. This is prevented by the ad- 
dition of a small quantity of lime, which neutralizes acids 
and coagulates impurities ; the lime is afterward precipi- 



LN1 SI GAR 

rbon dioxide, The juioe is evaporated bj boil- 
md, * hen redu( 
con olers, w here a portion of it 

I >n an avera 

lOD Of j pound Oi 

re purified, or refined, bj reducing them 
to a sirup, which Lb heated together with serum of bl< 

ie boiling-point The coagulating albumen 

.1 impurities, to remove which, and at 

tiif same time to d< nrup, il is again BItered 

through a I lered bone-black or animal 

• 1 in vacuum-pans the air 
hat it will boil at a lower temperature — 
and finally dlized. The drainage of the nw 

j, which is employed for culinary purposes 

and for the preparation mel. Bui of la: bod 

ived by which it is possible to gain nearly 

all the suga inc«l in mola>.-cs. It i> hoilc.l with an 

• ium hv«lr;i- thereby separating 

as a heavy. Ban . which, being ool- 

dioxide, is decomp 
strontium carbonate and orystallizabl 
sugar has a Bpecific gravity of L*( . able 

in about one third of it i\ of cold wa< ming a 

thick sirup. from concentrated solution- in 

or modified torn 
: solidities, on cooling, to a trai 

uhi«h, howi d turn- opaque 

Hi .:-k- 

I 

olic li«jn- 

ne-eugar 

lint of rotation 

pan [t ■:■■• - d 
directly, h 

it 



314 DESCRIPTIVE CHEMISTRY. 

mixture of dextrose and lsevulose (invert sugar). An 
alkaline solution of copper sulphate is not reduced by 
cane-sugar at first, but after boiling some time the separa- 
tion of cuprous oxide begins. 

519. Lactose, C 12 H 22 O n (Milk- Sugar), is found only in 
milk, to which it gives the sweetish taste. It is obtained 
by evaporating clarified whey till it crystallizes, forming 
quadrangular prisms containing one molecule of water, 
which it loses when heated. It is much less soluble, and 
therefore much less sweet, than cane-sugar, and its crys- 
tals are hard and gritty. It is much used in the prepara- 
tion of homoeopathic medicines. It does not immediately 
undergo fermentation, when brought into contact with 
yeast ; but after some time fermentation sets in. Eotten 
cheese, by a particular kind of fermentation, converts 
milk-sugar into lactic acid. Alkaline copper solution is 
reduced by milk-sugar. Maltose, the sugar originating 
from the action of malt extract, or diastase on starch, 
crystallizes with one molecule of water, like milk-sugar, 
and also reduces copper solution. It is the sugar formed 
in the process of making beer, and afterward converted to 
alcohol. 

520. The Amylose Group of carbohydrates includes 
substances of very unlike physical and chemical characters, 
partly of amorphous and partly of crystalline structure. 
They are derived from the glucoses by abstraction of a 
molecule of water. 

521. Starch, O 6 H 10 O 5 . — This substance is found uni- 
versally distributed in the vegetable kingdom in seeds, 
grains, roots, and the pith and bark of plants. When pure 
it is a snow-white, glistening powder. Examined by the 
microscope, it is found to consist of exceedingly minute 
round or oval grains, which vary in size from y^ to xo^o o 
of an inch in diameter. The starch-granules of potatoes 
are much larger than those of wheat or rice. Starch- 
grains from different sources vary also in form and struct- 



ROD 

Those of the potato are egg-shaped ; those of wheal 
I j those of rioe angular ; win! 




n 




>■-■■ , ■; ®> 

Fiq. 154.— Starch- Grains of Potatoes. 

oentrio 
to, like the la of an onion. As each farietyhas 

some peculiarity by which it may be identified, the adul- 
rheat-flourbypoti 

es may thus • «v ^A I^>^ 

starch U 1 in different \ c ^ ■»* 4 • 

in kneading the powdered c fc \j* *^£ #•© 

maeh«Ml material on ader • 

UtlllUoli : 01 W: 

itarch passrs tin- _ r luten and oeWnlar 

ihind. I ad the water u ponn d 
off. 

522. Properties and Uses. Starch ii insoluble in oold 

Lol, au<l 

paste in water oontainii alkali 

If beat ' '11 and 

icing a jelly-like mass | 
nae<i to impart a l'Ioss to c< r clothing. I 

test for FtuT . which ritfa it. formi 

a bl 

luminous so . as in 

Important : 



316 DESCRIPTIVE CHEMISTRY. 

starch which they contain. When vegetable food is pre- 
pared for the table by the various processes of cooking, the 
starch is slightly modified. Great quantities of starch are 
consumed in the production of dextrose, called in com- 
merce by the general name glucose. 

523. Dextrin. — When commercial starch is heated un- 
der pressure to 205° C. for some hours, it becomes soluble 
in cold water, and is changed into a gummy substance 
called dextrin, which, under the name of British gum, has 
been successfully substituted for the more costly gum- 
arabic by calico-printers in thickening their colors. Dex- 
trin is a mixture of several isomeric substances, and is 
also produced when starch-paste is boiled for a few min- 
utes with weak sulphuric acid. It is a transparent, brittle 
solid, isomeric with starch, soluble in water, incapable of 
fermentation, and produces right-handed rotation in a ray 
of polarized light; hence its name. When solutions of 
dextrin are boiled with dilute acids for some hours, the 
dextrin is converted into glucose. Dextrin is also formed 
from starch, by the action of animal secretions such as 
saliva, bile, and pancreatic juice. Starch which is insolu- 
ble, must be converted into soluble dextrin and sugar be- 
fore it can be assimilated by either plants or animals. 

Lichen starch, inulin, and glycogen are varieties of 
starch found in certain plants and animals, which differ 
from the common variety in some of their properties. 

524. Gums. — These are substances which are often 
seen exuding in globular masses from the bark of trees, as 
the plum and cherry. Gum is translucent, tasteless, in- 
odorous, and either dissolves in water, or swells up and 
forms with it a thick, sticky liquid, or mucilage. It exists 
in small proportion in the cereal grains, but its chief 
source is certain tropical trees, from the bark of which it 
flows in such quantity as to be gathered for commercial 
purposes. Arabin (C 6 H 10 O 5 ) is the important constituent 
of gum-arabic, the product of a species of acacia, which is 



! 1 1 7 

a hard, brittle . and ia, perhaps, th- 

of the commercial gums. Gum-arabic Lb used in pn paring 
medit r thickening colon, to hold the insoluble tan- 

• nded in ink, for making mucil 

//' i- Found in gum- 
tragacanth an<l base ad in cherry- 

gum, and other plant jui 

525. Cellulose (( !1 : < > >. . Tl bundant 
produ .' ion. B the chief bulk of 
wood. ■ raw and stalks in, in the 
neml iich envelops the kernel (bran), in the husks 

nd in tl 

fruit. ( ellulose is th< of the woody tissue. 

526. Properties and Uses. The properties of cellulose 
may be conv< uiently studied in fine linen and cotton, 
which are almost entirely d pure il 

and alcohol. Proloi 
extrin. Filter-] 
immersed for a Bhorl time in a mixture of concentrated 
sulphuric acid with half its volume of water, then washed 
with i inch like parchment. I' 

The uses of cellulose 
It f< oik of \. 

of linen and cotton fa rriting, printing, 

Rapping pap :' unaltered oellul 

a multitud ful chemical bo m its 

decomposition ; charcoal, illuminating gas, 

i < pa] i 
from it. 

527. Pyroxylin. If cellulose in tl 

l of th« 

of these 

- 



318 DESCRIPTIVE CHEMISTRY. 

is formed, which may be represented by the formula 
C 6 H 8 N 2 9 . A solution of this substance in a mixture of 
alcohol and ether is collodion, with which the glass plates 
used for photographic negatives are coated. When the 
solution is poured over a piece of glass, the menstruum 
quickly evaporates, and a translucent film of di-nitro-cel- 
lulose is left adhering to the glass. Collodion is also used 
like court-plaster to protect wounds from the air. Tri- 
nitro-cellulose, or gun-cotton, is formed when more con- 
centrated nitric acid is used. In appearance it is scarcely 
different from the raw cotton or other material from 
which it is made. Its empirical formula is C 6 H 7 N 3 O n . It 
is insoluble in water, alcohol, or dilute acids. By rubbing 
it is made strongly electric. Its most important property 
is its violent explosive quality. When lighted, it burns 
quietly, but if struck or jarred it explodes with several 
times the force of gunpowder. It does not explode when 
wet. It is used for filling torpedoes, and to some extent 
for blasting, but is not adapted for charging fire-arms, as 
the suddenness with which its force is exerted is liable to 
burst the piece. Under the name of celluloid a mixture 
of pyroxylin and camphor has found extensive application 
as a substitute for ivory, bone, and wood in making many 
small articles. It is plastic at a slightly elevated tempera- 
ture, becoming hard when cold. 

528. Fermentation. — Numerous compound substances, 
derived chiefly from plants and animals, when exposed to 
the action of air and water, at a given temperature, un- 
dergo decomposition, which, when involving the formation 
of useful products, is generally known as fermentation, 
but when resulting in the production of useless and ill- 
smelling bodies, is distinguished as putrefaction. These 
changes all agree in having a peculiar self-sustaining and 
contagion-like character. The true nature of the process 
is not yet thoroughly understood. The exciting cause of 
fermentation has been sought in the oxygen of the air, but 



FERMEN PATION, 

oars from experiments t hat air which ha 
passed through a red-hot tube does not induoe fermen- 
a been proved, however, that ordinar] air 
lopio planti and animal-, 

: lain that tin* pr« ilur to their action. 

529. Ferments and Fermentable Substances. Thesub- 

tion are certain oom- 

indfl rich in nitrogen, contained largely in Besh, hi 1, 

cheese, milk, whil gelatin, and other animal 

ducts. Th< - alj the | of wa- 

of air at the commencement, to induce 
in thrin a ] composition. Of those compounds 

which contain do nitrogen there arc hut few, as, for exam- 
ple, gum, and March, thai may be brought into a 
te of ferm< ntation by m< with air and water. 
But many incapabl rmenting by them- 
that change when brought in contact with 
[uantit] mentioned i 
bo«l •• latter are, for this reason, termed 
former > 

As a spark may kindle a conflagration BO the mini 
quantity of fermenting or putrescent matter is often Buffl- 

ile sub- 
markable communicability of thest i 
; in the action of yeast upon dough. I 
ako painfully illustrate.! by physiciai Bometin 

ind the while dissretilii of 

osing matter f: which cl 

• estahli^h a raj 
. which, in n 
quick ith. 

• of 

stances • which li 

nut 



320 DESCRIPTIVE CHEMISTRY. 

stomach of a calf) may curdle the casein of a great cal- 
dron of milk, or convert it into an insoluble modification 
(cheese). More instances in the following pages will show 
that we have to distinguish between fermentations caused 
by living organisms and those produced by unorganized 
ferments. Fermentation includes a variety of processes 
of very different nature, and these are, moreover, very 
much modified by temperature and other physical condi- 
tions. The kinds of fermentation best known are the 
vinous, acetous, lactous, and saccharous. 

530. Yeast. — The part played by yeast in fermentation 
has been a matter of much speculation. Yeast consists 
of round or egg-shaped cells about - 1 * of a millimetre in 
diameter ; these consist of an outer wall of cellulose, in- 
closing a liquid. The yeast-cells grow and multiply in a 
fermenting liquid, but the presence of nitrogen, phos- 
phorus, sulphur, potassium, and magnesium, in combined 
form, seems to be necessary to their growth. 

531. Vinous Fermentation. — When the juice of fruits 
or plants containing grape-sugar is exposed to the air at 
the temperature of 25° C, in the course of a few hours a 
change commences; small bubbles consisting of carbon 
dioxide rise to the surface, the liquid becomes turbid, and 
begins to ferment, or, as is commonly said, to " work." 
After a time the bubbles cease to rise and the liquid is no 
longer sweet, but has acquired a spiritous taste. If it is 
distilled, ethyl alcohol is separated, which has been pro- 
duced by the decomposition of sugar. Besides the alcohol, 
the fermented liquid generally contains two other sub- 
stances, namely, glycerin and succinic acid. Other com- 
pounds are also in some instances produced. 

532. Saccharous Fermentation. — But sugar itself may 
be a product of fermentation. When seeds are exposed 
to air and moisture at a suitable temperature, germina- 
tion commences. This consists in a series of changes, of 
which the first is an alteration of a portion of the nitroge- 



VTXEG \n. 






r and the production ol a compound nol well 
uii'i an active an- 

nt, whicl pon the Btaroh, chai 

it to sugar and dextrin. When barlej ted in this 

ira; and 

half an inch long the pn topped by heat, bul the 

533. Acetous Fermentation. If the rinoua ferment* 

; tin' liijuid l«»ses 

. and the 

oiilv l»v :nMiiiL r -'-me 
which al 

' 'y 

- a 
:ind of 

win 

which a 
as a fen I be 

I- W. Xfif ^r^t 

act* a* a carri* : ^ ^mm ^^"^ 

Fw. W7.-Vlncgmr OunrraUrt 

thus 

! 

■ 

within r 
is coiiin 




322 DESCRIPTIVE CHEMISTRY. 

tained from molasses to trickle through shavings in high 
tubs called generators, through which the air circulates. 

534. Organic Acids. — All acids derived from the me- 
thane group of hydrocarbons contain the univalent radical 
carioxyl ( — COOH), linked with a methane radical, or 
residue. Homology in many of them is as evident as in 
hydrocarbons and alcohols, as is seen in the following 
members of the series of " fatty acids " : Formic acid, 
H.COOH, Acetic acid, CH 3 .COOH, Propionic acid, 
C 2 H 5 .COOH. 

Acids originate from their respective alcohols by the 
replacement of two hydrogen-atoms by one oxygen-atom : 
CH 4 0, Methyl alcohol, becomes CH 2 2 , Formic acid. Ac- 
cording to the numbers of hydrogen-atoms replaceable 
by metals or compound radicals, there are mono- and 
poly-basic acids ; the relation of acids to salts is explained 
by the formula : 

Formic acid, H . COOH Potassium formate, H . COOK 
Oxalic acid, COOH Potassium oxalate, COOK 

COOH COOK 

535. Monohydric Acids. — The best-known organic acid 
is Acetic Acid (C 2 H 4 2 ). In the dilute state of three to four 
per cent, it is contained in vinegar, and this is obtained either 
by dry distillation of wood (wood-vinegar), or by acetous 
fermentation of alcohol, or spirituous liquids (533). The 
pure acid is prepared by neutralizing vinegar by sodium 
carbonate, evaporating the liquid to dryness, and heating 
the residue to about 250° C. Impurities are destroyed by 
this process, and the sodium acetate remaining is distilled 
with sulphuric acid. The distillate is acetic acid : 

2C 2 H 3 Na0 2 + H 2 S0 4 = 2C 2 H 4 2 + Na 2 S0 4 . 

Pure acetic acid is at ordinary temperatures a colorless, 
intensely sour liquid, having a pungent odor, and capable 
of raising a blister on the skin. It solidifies at or below 



THK FATTY ACIPS. 

italline body— glacial acetic add — and h 
aft 118° C. 

dilute f<>rm afl vinegar. It pns>esses in a hiirli 
the pit ion, and th< 

immoD tabl - 1- by 

inu them in vin< 

'.vent f«»r copper and load, contact with 
made of these metals should always 11] avoid 

hnioal ami medical im- 
»wii by the w 

' I . the firs! member of t! 

of fat: J md in main .»f animals and 

plants. [I tained by distill] ants | / 

[| ma] b artificially pi 
par. lyl alcohol and , d other 

ways. In many of its properl tcicL 

lUn is allowing 

mixture ol chalk, and eheese to ferment, h 

iall quantity in batter, in perspiration, u 

into, in the juice of human flesh, 
odor of rancid butter. The Be 
to i i>t of butyric arid. 

536. Higher Acids of the Fatty Series. —A 
to b ibera of the series, the higher the meltil 

an-; _ -points becom. . Beginning witl 

whi rdi- 

nary t« tanl of them 

:m the hulk of I 

. fats. Prom the tad thai fata an 
salts of tin tie- u ) 

ip of hydrocai 

oil. 



324 DESCRIPTIVE CHEMISTRY. 

537. Fats and Oils. — Besides glycerin stearate, and pal- 
mitate, most fats and oils contain the glycerin salt of oleic 
acid (C 18 H 34 2 ). These compounds are also called re- 
spectively stearin, palmitin, and olein. Fats and oils are 
combustible in air, have a smooth, slimy feel, are insoluble 
in water, but soluble in alcohol and ether, lighter than 
water, and make a peculiar stain on paper. When pure 
they are colorless, odorless, and tasteless. The fixed oils 
can not be distilled. When heated above 300° C, they 
are decomposed, giving off a smoke of a pungent odor due 
to acrolein. Their stain on paper can not be removed by 
heat. The other class of substances called oils (volatile or 
essential oils) are turpenes (572). Fixed oils are found 
in plants and in animals. Some vegetable oils have the 
property of " drying " or solidifying to a transparent mass. 
This depends on the presence in the oil of linoleic acid 
(C I6 H 28 2 ), which causes the change by absorbing oxygen 
from the air. Linseed (made from the seed of flax, linum), 
poppy, hemp, and nut oils, are drying oils. It is this prop- 
erty which makes them suitable for painting. The drying 
proceeds more rapidly if the oil has had a small quantity 
of lead oxide (litharge) dissolved in it while hot. Oil , 
which has been treated in this way is called boiled oil ; oil 
in its natural state is called raw oil. Non-drying oils ex- 
posed to the air commonly become rancid ; they are de- 
composed, losing their oily character and acquiring a dis- 
agreeable odor. This change does not occur in pure oil, 
but is brought about by the decay of albuminous matters 
usually present. Olive (sweet) oil, rape-seed oil, and mus- 
tard oil are non-drying oils. 

538. Soap. — When stearin, palmitin, and olein, the 
compound ethers of which fats consist, are acted upon by 
strong bases, salts are formed which are termed soaps, and 
the process by which they are produced is called saponi- 
fication. A decomposition takes place, the bases com- 
bining with the fatty acids, while glycerin is separated : 



uisnra 

0H= -.«...( 11 

St* .ite. Hum ■taan 

soap depends chiefly upon its alkali. 
ixtcure i and 

, while U 

it h this ; and consequently 

which renders the Boap liquid. The 
quality of hardness partly due to th< 

the at The compounds containing a large pro] 

rin,like tall* hard Boaps, while those in 

whi . as the Bofl fats ao 

a which is 
i» also adds to it- fluidit; B ip lias a 
powerful affinity for n i may retain from lift 

:it <>f it and .-till continue solid | 

i it in damp places where it will i 
in weight 1* ia solul in fresh water, hut, with the i 

ition of cocoanut-soap, is insoluble in Ball A -«»ft 

BOB]' by the addition of 

salt. / tiade bj dissoh u 

lmt alcohol, then allowing the Bolutioi 
- a kin«l in whi( 
ntaining th- 
le from olive-oil, h oth 

stearin and pal mi tin a- well a- oleuL Tl 

of iron in the » 
an impur 

i 
539. Action of Soap in Cleansing A 
•stance-. 

I 
which 

with f.t 



326 DESCRIPTIVE CHEMISTRY. 

of fat in order to combine with its acids. Hence the soap 
acts upon the oil during ablution, partly saponifies it, and 
renders the unctuous compound freely miscible with water, 
so as to be easily removed. The cuticle or outer layer of 
the skin is chiefly composed of albumen, which is soluble 
in the alkalies. The alkali of the soap, therefore, dissolves 
off a portion of the cuticle with the dirt ; every washing 
with soap thus removing the old face of the scarf-skin and 
leaving a new one in its place. The action of soap in 
cleansing textile fabrics is of a similar nature. Alkalies 
not only act upon greasy matter, but dissolve most organic 
substances. In the case of soap, however, the solvent 
power of the alkali is in part neutralized, thus preserving 
both the texture and color of the fabric. The oily nature 
of the soap also increases the pliancy of the articles washed. 
540. Polyhydric Acids. — Acids which may be regarded 
as derived from polyhydric alcohols are called polyhydric 
acids. Either one or more of the CHoOH groups may be 
converted to a CO OH group, so that a polyhydric acid 
may be monobasic or polybasic : 

COOH 

CH 2 OH COOH CHOH 

COOH COOH COOH 

A dihydric A dihydric A trihydric 

monobasic acid. dibasic acid. dibasic acid. 

Lactic Acid, C 3 H 6 3 . Two modifications of this di- 
hydric acid are known, ordinary and sarcolactic acids, 
offering only optical differences. The first is prepared 
by a fermentation similar to that of butyric acid (535), 
but interrupted at an earlier stage. It is this acid, to 
which sour milk and " sour-kraut " owe their taste. In a 
pure state it is a colorless, acid sirup, which destroys ani- 
mal tissue by continued contact. Sarcolactic acid and 
salts of it are found in muscular fiber. 

Oxalic Acid (C 2 H 2 4 ) occurs in sorrel, rhubarb, and 



I HYDRIC H 

plants, and may be artificially prepared in 
ways. Fon i^ was L by nitrio acid, 

and the solution whereupon oxalic i 

resent it i> produced on i lai by 

si with causi ( txalic add is poison- 

-. and ite psom Baits, for 

•h it is mes mistaken. In 

ilk or magnesia, mixed in water, is the proper 

in calioo-printii 
it is also employed as a delical 
lime, with which il an insoluble Bali It r< 

ink and iron -tains from linen by formings Boluble oxa- 
• the acid i> injure the 

immediately removed by washing. [I power 
to i :' the m< soluble oxalates 

it useful for f«»pj»«T. 

atation i 1 by the distillation of 

rtain n . and in 

small quantities in animal juioes. Intimately oonned 
with this acid 3 n hich follow : 

found in many acid fruits and in 

of rhubarb, hut is usually i I from I 

unri iee of the mountain-ash. It is a col lid, 

dissolves readil] d alcohol, and crystallizes with 

solutions of all the arid- nanird ha\«- an 

agreeamY acid toldy if long kept, and 

gradually ui n. 

found abundantly in 
In the fen • as 

tses bitarl 

in alcol 

it with calcium car ium chl 

ul- 

the 



328 DESCRIPTIVE CHEMISTRY. 

acid crystallizes in oblique prisms. Potassium bitartrate, 
when purified, is called cream of tartar, and is a highly 
esteemed medicine. It is very slightly soluble in cold 
water, and an excess of tartaric acid therefore serves to 
detect the presence of potassium salts in solution, caus- 
ing a white precipitate. Potassium-sodium-tartrate, or 
Kochelle salt (KNaC 4 H 4 6 ,4H 2 0), is prepared by adding 
cream of tartar to a solution of sodium carbonate until 
saturated, and evaporating the solution. The salt sepa- 
rates in large rhombic prisms. It is the chief constituent 
of Seidlitz powders. If in cream of tartar (KHC 4 H 4 6 ) 
the first hydrogen-atom is replaced by the radical antimo- 
nyl (SbO), a salt is produced which, under the name of 
" tartar emetic," is the most usual medicine for causing 
vomiting. Citric Acid (C 6 H 8 7 ) is found principally in 
fruits of the orange family, but occurs also in gooseber- 
ries, currants, and other acid fruits. It may be readily 
procured from the juice of the lemon by the aid of chalk 
and sulphuric acid. It has a pleasant acid taste, is very 
soluble in water, and is used in medicine and for effer- 
vescing drinks. 

541. Amides. — Hydrogen in ammonia may be replaced 
by alcoholic radicals, amines resulting (512). By substi- 
tuting the radicals of acids, amides are produced. Acetyl 
(CH3.CO) is the radical of acetic acid, having the formula 
of the acid, minus hydroxyl. Substituting one atom of 
hydrogen in ammonia by acetyl, we obtain NH 2 C 2 H 3 0, 
acetamide ; by substituting the remaining hydrogen-atoms, 
di- and tri-acetamide are produced. Amides play a promi- 
nent part in the assimilation of food by plants ; they have 
been ascertained to be the generators of albuminous mat- 
ter. An important member of them is asparagin, widely 
distributed in germs of plants, and at first discovered in 
the shoots of asparagus. 

542. TJrea. — But the most interesting of all amides is 
carbamide, or urea, the amide of carbonic acid. It is the 



AMI 

chief pi - *ular fiber in the aj rten 

animals, and ifl « :li the fcridn< 

impared n itfa carboi 

artificially bj a method remarkable in t \% * ► 

• was the til" .1 |'iv|»- 

Qce "ih« i .ly knon d aa a prodaoi 

animal I an instance of the 

iito an isomer by simply evapo- 
\\ i □ •'! i- in. 

and minium, and the molten 
mas bed in : the composition 

K< SO (potassium - dissolved. When ammo- 

Diam-salpfa Ided to the solution, the following re- 

m takes ])la 

\<» - .Ml/ 80, .'MM SO ^ K - 

_ tin* liquid to dryness and extracting the 
residue by I . which on «■<»<. 1- 

erystals, which 
are exactly identical with naturally funned area Ammo- 
nium < u this ; ok 

arbamide, or ur 

MI ; ( INO I 0< v 

rtificia] area may jn 

ittainmenta of I 

the <»ld belief in a \ ital f<<' 
. the fact that the formation <»f • •••n.; 

in the li\ ;• a- well as 



330 DESCRIPTIVE CHEMISTRY. 

CHAPTER XXIX. 

THE BENZENE-DERIVATIVES, OR AROMATIC GROUP. 

543. Coal-Tar Products. — In the preparation of illumi- 
nating gas from coal, a black, viscid liquid, coal-tar, col- 
lects in the condenser. This by-product is the source of 
many compounds of the highest scientific interest and 
practical value. For their separation, the tar is at first 
subjected to distillation, and the products are collected in 
receivers containing water. The lightest and most volatile 
constituents which pass over first, and which float on the 
water, form what is called the " light oil" Substances of 
higher specific gravity follow, sinking to the bottom of the 
water; they constitute the "heavy oil" A black residue, 
called "pitch" remains in the retort ; it is used for roof- 
ing, concrete sidewalks, etc. The light oil consists mainly 
of benzene, toluene, xylene, and cymene — hydrocarbons of 
the aromatic series. The heavy oil, or " dead oil," con- 
tains carbolic acid, naphthalin, anthracene, analin, quina- 
lin, etc. 

544. The Benzenes. — The aromatic hydrocarbons, so 
called because of the fragrance of many of the series, are 
very stable substances, and are remarkable for their nu- 
merous isomers. The series begins with a substance con- 
taining six carbon-atoms apparently arranged in a closed 
chain or ring, and linked together alternately by one and 
two bonds, thus : 

H(l) 

i 






(6) 


H- 




s \ 
-0 0- 

1 II 


H 


(2) 


(5) 


H- 


-C 0- 

\ / 


1 


H 


(3) 






H (4) 

Benzene, C 6 H 6 . 





Till! BE* ;;;;i 

Th I member {( -IL> is derived from this by sub- 

_ l I i • be hydrogen-atoms, and eaob 

Deeding member is derived from the one preceding it 

by a similar substitution, either on the main ring or i - 

ain. The genera] formula is 4 M ,, Three isomeric 

products arc possible. If in beniene two 

hyd placed by methyl, substitution may 

hai ' 1 and - 1 ami »'» ; in this c;im' the 

in ortho-compound : it" substitution took place 

at I . oral l and 5, a meta-compound is formed; if 

two opposite places, such as l and -i. a para-compound 

results. All hydrogen-atoms in benzene may be substituted 

b] methyl; the homol< impounds thus originating 

I II 

M. thj (Tolu< I ( 6 II .( II 

Dimethylbenxeii I II. (< II ), 

Trimethylb ll< ritylene), I II (( II | 

ethylbensene 1 1 >un I . 1 1 1 1 1 1 ; 

ntamethylbenaei I JEL(( B | 

II (',((' I I,) t . 

;: l . // up. 

545. Benzene, or Benzol 1 1 J I >, nol to be confounded 

itained in rectifj ing petroleum, i- 

ally prepared by fractional distillation of a purified lighl 

coal-oil. I* can be further purift oling it below 

int of u.it'T, irhen it congeals, forming a 

leased and thus freed from im- 

• • can all ilt up fr<»m its elem< r, if 

■ 

;i heated to •! into I 

II, = (MI [t i a oolorlt- hut 
liquid ol ereal odor, I 



332 DESCRIPTIVE CHEMISTRY. 

water, boiling at about 80° C, and becoming solid at 5° C. 
It is inflammable, burning with a luminous flame. It is 
insoluble in water, but dissolves in half its weight of alco- 
hol, and is thus distinguished from petroleum " benzine," 
which requires five parts of alcohol for solution. Benzene 
dissolves iodine, sulphur, phosphorus, fats, and resins. 

546. Higher Hydrocarbons of the Benzene Group. — 
Toluene, or methyl benzene (C 6 H 5 . CH 3 ), the next member 
in the series, is also contained in light coal-oil. It boils 
at 110° C, and does not solidify at —20° C. A mixture 
of both hydrocarbons is used for the preparation of anilin 
colors. Higher members of the series are found in coal- 
tar ; some also have been artificially obtained. 

§ 2. Derivatives of the Benzene Hydrocarbons. 

547. However different the constitution of benzene 
may be regarded from that of methane, yet they are found 
to conform in several respects. As methane may be re- 
garded as the hydrogen compound of the radical methyl, 
so benzene may be explained as a corresponding compound 
of hydrogen with C 6 H 5 , phenyl, the radical of benzene. 
This conformity becomes apparent in some of their de- 
rivatives : 

Methylchloride, CH 3 C1. Phenylchloride, C 6 H 5 C1. 
Methylalcohol, CH 3 .OH. Phenylalcohol, C 6 H 5 .OH. 

(Phenol). 

548. Nitro-derivatives. — By the action of strong nitric 
acid upon benzene, one or two hydrogen-atoms are re- 
placed by the group N0 2 . 

C 6 H 6 + HN0 3 = C 6 H 5 N0 2 + H 2 
C 6 H 6 + 2HN0 3 = C 6 H 4 (N0 2 ) 2 + 2H 2 0. 

The compounds thus produced are nitrobenzene and 
dinitrobenzene. The former is a yellow oil, distinguished 
by a pleasant smell, resembling that of bitter almonds. It 



UODO-DERn AllVi 

much applied in perfumery, and is known by 
the name M Toluene und 

. I 1 1 i \< l i .< » 1 1 
i upon indigo, vario 

'imnuilv known 

in yellow, ahin- 

Dund application in dy< ol, 

.mi yellow c<»lnr. ( lol- 

Qg only B 1 animal or -liMin- 

I . strip of a tab] ich 

e immersed in a solution of picric acid, then 
. the woolen Btrip alone will appear yel- 
When heated, picric acid explodes violently. 

549. Amido-derivatives.— IMimvl and the higher radi- 
68 may replace an atom of byd 

-miliar to tl I be 

! 1 1 . 1 1. \ ! I ». the 

-• known of thei utained in the products of de- 

rition b] [ many organic compounds, [I 

uufactur fage scale by the i & reduci 

agents upoi whicb purpose iron or rinc 

Slings and hydrochlori m- 

-I thus e which i 

.nilin : 

:.\<> --ill ( .11. MI | -2H 0. 

[quid, rapidly becoming brown 
win and b 

I 10I- 

ubl< 1 with chloride of 

lime, assumes a purple-yiolel P tassium bichi 

a Bolution of anilin in sulphuri im- 

I ilin fori; 

and of I 

i from 



334 DESCRIPTIVE CHEMISTRY. 

lin designed for the manufacture of rosanilin, the mother- 
substance of anilin dyes, must contain toluidin, for it is 
not alone convertible into rosanilin. 

550. Anilin Dyes. — When a mixture of anilin and to- 
luidin is treated with oxidizing agents, such as arsenic 
acid, Rosanilin (C 20 H 19 ]N"3) is formed. This is the base of 
all real anilin colors, while under the same name are fre- 
quently used a variety of other coloring compounds de- 
rived from coal-tar. Eosanilin is colorless, and may be 
obtained as a hydrate in white crystals by adding sodium 
hydrate to one of its salts. By traces of acids, however, 
even by atmospheric carbon dioxide, it turns red, forming 
crimson salts soluble in alcohol and water. Fuchsine, the 
hydrochlorate of rosanilin, crystallizes from concentrated 
solutions in green crystals of metallic luster. Its best 
solvent is alcohol. Fuchsine, as well as the other rosani- 
line salts, may be applied directly for dyeing wool and 
silk ; vegetable fibers, on the contrary, have at first to be 
treated with some mordants, such as aluminum acetate, 
or " tin salt." Eosanilin salts, by reducing agents, are con- 
verted into colorless salts of leuhanilin (C 20 H 21 N 3 ). By 
means of sulphurous acid anilin-stains can be removed. 
There are various blue, green, yellow, and violet anilin 
dyes in the market, which are products of substitution of 
hydrogen-atoms in rosanilin by other radicles. Analin- 
Uack is a base of doubtful constitution, obtained as an 
amorphous precipitate by the addition of potassium chlo- 
rate, or permanganate to a rosanilin salt. Anilin colors 
are also produced naturally. Aplysia, a shell-fish, secretes 
a concentrated solution of anilin, red and violet, for its 
protection against pursuit. The red and blue stains fre- 
quently observed in various kinds of food seem to be due 
to the formation of similar compounds by putrefaction. 

551. Phenols and Aromatic Alcohols. — Substitution of 
hydrogen-atoms in benzene and its homologues by hy- 
droxy! produces two series of compounds, phenols and 



QARBOUG a< 11' 

isomeric, and their 

vrhether substitution i<».»k place in 
the benzene ring or in tin* lateral chain. Thus oresol and 
benxy] alcohol are isomeric, both haying the empirical 
formula c : IU>. but their rational constitutions differ, 
B8Bed by the formulas — 

C Qt.OH.OB ( 11 < II. Mil. 

OeaoL 

Th< Is to which oreeol belongs exhibit greal dif- 

ferences from aromatic aloohols ; the] are nol convertible 
into aldehydes and acids, hut have themselves an acid 
Icohols, on the contrary, may be 
transformed into aldehydes and acids. 

552. Phenol iLAlcok 

of the chief constituent el-tar, and 

Iso found in the products of dry distillation of iroi 

heated, is split up into phenol and 
carbon di 

( -II - 00,+ I H nil. 
Pb noL 

Seav] oil of coal-tar is the chief source of phenoL 
ion of phenol the oil is I w ith a 

lution of caustic soda, vrhereby phenol and it- homo 
are dissolv. < ide phenol, by addition ilphuric 

acid, rises to the top and is rem It is then iubje< I 

to fractional distillation; the distillate, 

phenoL When purr, phe- 

TtalllBffl at Ordil -lories."*, 

n&- ms, whicl om the 

oily h 
md boil ire soluble in 16 

10L 'I >ky 

odo: rid taste. I Idn 

y produce blisters. I Mi 



336 DESCRIPTIVE CHEMISTRY. 

the property of preserving animal substances from decay, 
and solutions of it are on this account much employed as 
antiseptics. It is a poison to animal and vegetable life. Ep- 
som and Glauber's salts, in large doses, are antidotes for it. 
553. Disinfectants. — Disinfection includes two oppo- 
site processes : the hastening of decomposition and the 
prevention of decomposition. Disinfectants which hasten 
decomposition do so by promoting the action of oxygen, 
thus rapidly burning away harmful gases and putrefying 
matter to harmless products, and are called deodorants. 
To this class belong chloride of lime (216), charcoal (315), 
earth, lime, and potassium permanganate. Antiseptics 
prevent putrefaction and similar changes by killing or 
stopping the development of the germs which cause them. 
Of this sort are sulphurous, chromic, acetic, carbolic, and 
other acids, heat and cold, sulphates of zinc and iron, 
camphor, turpentine and other volatile oils. Air and 
water are mild but often effective disinfectants. For 
purifying the air of a room, only volatile disinfectants 
are of use, such as chlorine, sulphurous and carbolic 
acids, and volatile oils. A room can not be thoroughly 
disinfected while it is occupied. If sulphurous acid is 
used, 1£ ounces of sulphur for each 100 cubic feet of 
space must be burned. To disinfect clothing, the articles 
may be boiled in water and then steeped in a solution of 
carbolic acid (4 ounces of " liquid " acid to a gallon) ; a 
more thorough method is to subject them to the action of 
sulphurous acid and then for six hours to a temperature of 
120° C. Chloride of zinc and strong carbolic acid must 
not be used to disinfect clothing, on account of their cor- 
rosive action. Lime is the best disinfectant for stables, 
having a cleansing as well as an oxidizing effect. Sub- 
stances are frequently sold as disinfectants which are 
neither oxidizers nor antiseptics. They only hide one bad 
odor by producing another, and are therefore worse than 
useless. 



554. Creosote is a varying mixture of phono! with 

, which arc higher Immn Indues of phenol, ami 

ha\ ion I :H,< K li i- oontained in pj 

is acid, and is preps phenol 

-tar. The portion of the tar distilling at ab 

1. The preei property of the 

r the mod pari be ascribed to the 

- colorless, i»ut soon 

to air j it hai og and 

ad is a powerful antiseptic 

555. Pyrogallol M.IIioli i trihydrie alcohol, 
tl»lc a> a redncii *. It is easily dissolved by 

can- rapidly abeorbii pen and 

lack. [I ia therefore applied tor the determi- 

*■•>. I • • . — -liver from its Baits, 

as a M «i n in photography. It 

iblima- 
d, and condenses in long, white, prismatic cr 

556. Benzyl Alcohol 1 1 . 11, ( II. nil ).— In balsai 

and Tola compoui na of this alcohol occur natu- 

rally. It U product of the action of reducing 

ag* ad bensoic acid, and ma] 

• these compounds by oxidixii 
»hol is a colorless liquid, of i pleasant aromatic 
odor. I tthol, the hydroxy! being sub- 

stitute in t.. hain (-('II -' >E |. 

557. Aromatic Aldehydes. - -Tl mpounds stand 
in I as aldefa 

C\H«0 I ihol 

is { which 1 

been n It is 1 

rcoside i rod in the 

leaves, bark, and frui* 
pin: thus prepai . - «-«»n- 

15 



338 DESCRIPTIVE CHEMISTRY. 

tains hydrocyanic acid, and is therefore poisonous, but, 
when freed from this impurity, benzoic aldehyde is harm- 
less and largely used in perfumery. It is a colorless liquid, 
of a pleasant, almond-like odor, boiling at 180° C. Sali- 
cylic Aldehyde, or Salicylal (C 7 H 6 2 ). — The same relation 
existing between benzyl alcohol, benzoic aldehyde, and 
benzoic acid, is also observed between saligenin, salicylic 
aldehyde, and salicylic acid. Saligenin, by a kind of fer- 
mentation, originates from the glycoside salicin, which is 
found in the bark of willows. By oxidation it is con- 
verted into salicylal, which also naturally occurs in the 
flowers of meadow-sweet. It is synthetically prepared by 
the action of chloroform on an alkaline solution of phenol : 

C 6 H 5 HO + CHOI3 + 3KHO = C 7 H 6 2 + 3KC1 + 2H 2 0. 

Phenol. Salicylal. 

It is a fragrant oil, which, by boiling its alkaline solution 
with cupric oxide, is converted into salicylic acid. Vanil- 
lin, the odoriferous principle of vanilla-beans, is also an 
aldehyde of the aromatic series. It is artificially prepared 
by the action of chloroform on guajacol, a dihydric phenol. 

558. Aromatic Acids — Benzoic Acid (C 7 H 6 2 ). — This 
product of oxidation of benzyl alcohol and of benzoic alde- 
hyde occurs native in gum-benzoin, which is the chief source 
of it, in various other gum-resins, and in Peru-balsam. 
Benzoic acid is a white solid, little soluble in cold water, 
very soluble in alcohol and ether. It has an aromatic 
odor, and its fumes are strongly irritating to the respira- 
tory organs. As a remedy for internal use, however, it 
acts as a powerful solvent in affections of the lungs. 
Benzoic acid is produced in the system of vegetable-feed- 
ing mammalia and secreted in combination with glycocol 
as Mppuric acid. 

559. Saccharin, or Ortho-sulphamin Benzoic Anhydride 

CO 
(0 6 H 4 <oq >NH), is a derivative of benzoic acid, which 



SALICYLIC \< il> 

•me no important artiole of commerce. It 
was discovered in the laboratory of the Johns Sopki 
XJii Baltimore, and is distinguished bj an wi- 

sely sweet taste, by far surpassing that of any other 
stance known. Having also been found perfectly harm- 
less to the human Bystem, it is likely bo beoome i valuable 
ins for improving the tastes of various industrial prod- 
is well as of medioii 

560. Salicylic Acid M : 1 I,n,) OOCUTfl naturally in the 
flowers of meadow- associated with salioylaL lie- 
thyl-salicylate is the chief constituent of the nanontial oils 

of win' d and birch, both of which arc extensively 

in this country for perfumery purposes. Sali- 
cylic acid may be prepared from salicylal and saligenin 
by oxidation; but the principal way of manufacturing it 
consists in introducing carbon dioxide into sodium pheno- 

• The pp 'i a 

tple addition of carbon dioxide, as expressed by the 

( .if ONs h 00,= I -H \a. 

BB phenolate. Sodium 

The sodium sali<\ then dissolved in water and 

sal: rated by addition of hydrochloric arid. 

Salicylic acid is a whil owder, little B liable 

in water, bi Boluble in alcohol and ether. It is a 

dihydric acid. Ferric chloride im] in- 

color to it- aqu< ition, by whicb n 

v be ascertained. B I is 

an important n for 

rful 
antisepv ititios. 

561. Gallic Acid 1 1 . Il,< » i. I 

reduce- mni of 

^all-nuts, receive* 1 the i 
stallizes in . white i 



340 DESCRIPTIVE CHEMISTRY. 

water and alcohol as well as by ether. Ferric chloride 
produces a bluish-black precipitate in its solutions. When 
heated it is broken up into pyrogallol (555) and carbon 
dioxide. In a series of compounds known as tannic acids, 
or tannins, gallic acid is combined with glucose and simi- 
lar bodies. 

562. Tannic Acids are extensively diffused throughout 
the vegetable kingdom, and are all distinguished by an 
astringent taste. The bark and leaves of most forest-trees, 
as well as of many fruit-trees, contain a large quantity of 
tannin ; it is found in various roots, shrubs, and seeds, and 
is the astringent principle of tea and coffee. They are 
all precipitated by ferric salts, the precipitates being either 
black or green. They also precipitate solutions of glue, 
and combine with animal tissues, forming insoluble com- 
pounds (leather). 

Gallotannic Acid, or Tannin (C 27 H 22 17 ), is found in 
large amount in nut-galls, in oak-bark, and in sumach. It 
may be obtained from gallic acid, by substances withdraw- 
ing water, and on the other hand may be converted into it 
by boiling with dilute acids. The usual method of pre- 
paring it consists in extracting powdered nut-galls by a 
mixture of alcohol and ether. Gallic acid and extractive 
matters dissolve in the ether the tannic acid dissolves in 
the alcohol. By evaporation of the latter the product is 
obtained as a yellowish, amorphous residue, soluble in wa- 
ter and alcohol, but not in ether. In concentrated aque- 
ous solutions of tannin, ferrous salts produce a gelatinous 
white precipitate of ferrous tannate, which by contact with 
air becomes dark-blue. Ferric salts give at once a blue- 
black precipitate, which may serve as evidence of their 
presence. Writing-ink is commonly prepared by dissolv- 
ing ferrous sulphate in a decoction of nut-galls, adding 
gum-arabic to thicken it. On account of the white color 
of ferrous tannate, ink generally has to stand for some 
time exposed to the air before it has darkened enough to 



rrous tannate during this time la dowly oxi- 
tannafa latter is bo finely dii i< 

light, as to remain suspended in the liquid tor a lo 
tin .in, by . i and oonl i proper- 

s, finds frequent application in medicine f*>v external 
as well aa internal S soluble precipi- 

> with metals and other injurious sub- 

noes, it prOYefl Useful in many « -ases as an antidote. 

563. Tanning. By far the most important property 
of tannin is that of transforming animal akin into leal 

— that is, of rendering it durable and in a high degi 
resi mechanical and chemical action. All animal 

Mies, as well as albuminous matter, L r iv«- insoluble com- 
i tannin; its compounds with skin are called 
: the process of producing them is called ( 
d by first Boaking the In 
for several • . milk of lime, by which treatment the 

osened and the fat is Baponified. The hi 
are thei t into a bath of very dilute Bulphuric acid 

(1 to 1,000), which - the adherent lima Then the 

hides are si in infusions of oak-bark, 

h of whirli is gradually in< Teased. This tivat- 

. tinned for about >i\ when the hi 

ked into pita \n itb alternate layers of 
ground irk, which are then filled irith water; the 

treatment ; three month- 1. mother pit, 

hides being placed the other Bide up. Tl 
finished, when a section of the leather 

• be hide, bj abso 
increased from thirty • 

I goats, sumach 

564. Naphthalene Group. I titution of 

group of b. 



342 DESCRIPTIVE CHEMISTRY. 

contains two benzene-molecules linked together, so that 
two carbon-atoms are common to them both : 

H H 

i i 

C C 

H-C' X C 7 % C-H 

H-C C-H 

V x c^ 

i i 

H H 

Naphthalene. 

Naphthalene (0 10 H 8 ) is a product of decomposition by 
heat of benzene and various other substances. The prin- 
cipal source of its production is coal-tar, and naphthalene 
is found in the last part of the distillate obtained from it. 
If this part is collected separately and left to stand, a 
crystalline substance settles, chiefly consisting of naphtha- 
lene. By repeated sublimation it may be obtained per- 
fectly white and in large, colorless, brilliant plates, melt- 
ing at 79° 0. and boiling at 218° C, easily soluble in 
alcohol and ether, not in water. It has a faint, peculiar 
odor. Naphthalene has found successful application in 
medicine, and is considered an unexcelled destroyer of 
moths and other small parasites. 

565. Pyridine and Quinoline. — Among the numerous 
products of chemical decomposition contained in coal-tar 
are the compounds — pyridine and quinoline — and their 
homologues. In constitution they resemble benzene and 
naphthalene, inasmuch as pyridine is a benzene and quin- 
oline a naphthalene, in which one OH is replaced by 
nitrogen : 

H H H 

C CO 

s \ • \ / v 

HC OH HO C OH 

HC CH HO C OH 

\ y % / \ / 

N NO 

H 
Pyridine, C 5 H 6 N. Quinoline, C 9 H 7 N. 



AvniKu km: QROUP. 

Pyridine and its homologies an >btained from bone- 

oil, the liquid passim: over, when hones are suhjeetod to 
. distillation ; this liquid ifl also known by the name of 

u fetid animal oil." Hone-oil also contains quinoline and 

its homologues. Pyridine and quinoline arc of a peculiar 

:p odor; both compounds haw a strong alkaline char- 
acter. They arc belieYed to be nearly related to some of 
the alkaloid- occurring in nature (quinine, nicotine, etc.), 
►ped that these important bodies may yet he 

etieally prepared from cither pyridine or quinoline. 

The wh IS Of benzene-derivatives aflords numer- 

• •s in which products Of destruction of animal 
or vegetable matter may he utilized for protecting and 
pres human and animal life. 

566. Anthracene Group. -The products of the distil- 
lation of coal-tar, pa raral thehighesl temperafa] 

:itication, pressure, and crystallising from 

I .1 [*)« Its Constitution ifl ex- 
plained by the formula : 

0.B, g ,,,!., 

in which I scfa Bide represents no-ring. 

is also prepared by several other methods. 

It crystallize* incolorlec s, and boils at about 360 0. 

[uired technical importance as the ma- 
il forpr - artificial alizarin. By oxidising sgents 
1 into anthratj I JliO,), 

which crystallizes in yellow needle- and combines with 
• mine forming dibrom-anthra^uinone ( < J 1. 1 U \< >. ), by 
fusing which with potasHium hydrate slisarin rasull 

= M B (OH)/) | IS 

All/ • 

567. Alizarin, or di-oxy-anthraquinoni •>,), was 
Ion : fron the pool of madder, hut at 

BSSnt almost all rcial all. pared from 



344: DESCRIPTIVE CHEMISTRY. 

anthracene. Fresh madder contains no alizarin, but it 
contains ruberythric acid, a glycoside, which by a kind of 
fermentation is converted into alizarin, when the root is 
moistened. 

Alizarin has the character of a weak acid ; it crystal- 
lizes from alcohol in yellow-red prisms, sparingly soluble 
in water, readily soluble in alcohol. At 290° C. it melts 
and sublimes in orange-colored needles. It is generally 
brought into commerce in form of a paste. In alkaline 
liquids it dissolves with a purple color, and its solutions 
are precipitated by salts of aluminum, and tin with a pur- 
ple color, by ferric salts with a violet-black color. These 
precipitates are called madder-lakes, and it is on their in- 
solubility and permanence that the application of alizarin 
for dyeing purposes depends. 

Several artificial dye-stuffs are prepared from alizarin 
in a similar way as anilin colors are from rosanilin ; the 
best known of them are purpurin, alizarin carmine, and 
alizarin-blue. 

568. Cymene-Derivatives, — Among the higher homo- 
logues of benzene, Cymene, or methyl - propyl - benzene 
(C 10 H 14 ) is distinguished by a variety of derivatives, some 
of which are widely distributed in the vegetable kingdom, 
and are of practical importance. They may be subdivided 
into phenols, turpenes, and camphors. 

569. Thymol (O 10 H 14 O), the phenol of cymene, is a 
constituent of the oil of thyme and of various other essen- 
tial oils. Forming colorless crystals of an aromatic smell 
and of a peppery taste, it is frequently used in medicine 
as an efficient antiseptic. Unlike ordinary phenol, it is 
not poisonous. 

570. Turpenes are hydrocarbons occurring in most es- 
sential oils and in many resins. Their composition agrees 
to the formula C 10 H 16 , or to polymers of it. They differ 
from each other by their physical properties in general, 
and by their optical characters in particular. A relation 



I kliPHOBft 

p, in all of them, is prored by the fad 

that, by withdr two hydrogen-atoms, they all yield 

-■ turpentim consists chiefly of one of them, 

11). Tlu 1 oil is obtained bj d 

tilling pitch, a balsam nr natural mixtan DS and 

essential «»i; I by pine and lir tnrs. The residue left 

in the r . if retaining water ; or i 

ter. I dl of turpentine, i nn1 

power for n I other substances, and 

ts volatility, is much used in the manufact- 
ure of \ ii its. li al \\ gen trom the 
ral similar essential oils do, thereby acquir 
rful nxidi/.inir properties. 
571. Camphors. — The nan ; /"/* includes Bereral 

produced from 
rious plants, 'i ntain oxygen, and Are believed to 

\idati<»n. ( '<>m- 

□ camphor obtained by sublimation fin 

■ee belonj the laurel genus, and growing in china 

nan. It ton agonal crystals, melts at l ; 

boils al when ignited, burns with a r 

• k i 1 1 ir flame. It is somewhat volatile, even al oommon 
itures, is soluble in alcohol, hut Boaroelyso in iratet, 
i is esteemed an eff< ly for internal and i 

When heated with iodi verted u 

phenol : 

( ||,U+I.= I I; MM. 

unphor is proved to h the 

: to the group. Reduc- 

Hid 

JoohoL I is 

•r prepared from oil of bond 

tin. 



346 DESCRIPTIVE CHEMISTRY. 

572. Essential Oils, also called ethereal or volatile oils, 
are widely varying mixtures, most of them consisting of 
turpenes and oxygenated compounds, such as alcohols, 
aldehydes, phenols, camphors, etc. The expression " es- 
sential oils," therefore, does not precisely denote a definite 
class of chemical compounds. Most of them are obtained 
by distillation of parts of plants with water, some by press- 
ure. They are strong-scented and volatile liquids, pro- 
ducing a stain on paper, which disappears on warming. 
Thereby they are distinguished from fat-oils, and a fraudu- 
lent admixture of a fat-oil is easily discovered. They are 
sparingly but to different degrees soluble in water, readily 
soluble in alcohol. Many of them at low temperatures be- 
come solids of camphor-like character. Most of them are 
colorless and mobile when pure and fresh, but they become 
yellow and viscid when kept for some time exposed to air. 
They are the substances which give the distinguishing 
flavors and odors to many vegetable products. 

Some of them have a peculiar color; camomile -oil is 
blue, wormwood-oil is green. They are commonly classed 
as oils free from oxygen and oils containing oxygen. Oils 
free from oxygen are oils of turpentine, lemon, lavender, 
rosemary, and juniper. The oils of fennel, anise, cloves, 
peppermint, and thyme contain oxygen compounds besides 
terpenes. Allyl-sulphide (C 3 H 6 ) 2 S is the chief constituent 
of the oils of garlic and onions, and is also found in the 
seeds of certain cruciferae. Several so-called essential 
oils do not exist already formed in plants, but they are 
generated by a process of fermentation when the crushed 
parts of those plants are macerated with water. Thus, 
the oil of bitter almonds, benzaldehyde (557), is produced 
by the action of emulsin on amygdalin ; mustard-oil in 
the seeds of black mustard, by the action of myrosin on 
myronic acid; it has the composition C 3 H 5 CNS (allyl- 
sulphocyanide). 

573. Resins and Balsams. — Eesins are turpenes, which 



[NDIOO QROUP. ;;17 

haw undergone a change by oxidation. They are weak* 
resembling the acids of tin- fat t % aasmuol] 

ted upon by alkalies forming resin-soaps. Many 
of them, moreover, contain particular constituents. Ben- 

loin contains I ai - uccinic ioid; al«»e, 

<ams are natural solutions of ivmus in essential 

- with various admixtures. The best known of them 
turpentine, Peruvian ami oopaiba balsam. Own* 

ins, :n and essential oil, also contain iruin and 

mucilage. lndia-rnl>hcr and (juttd-percha are hydrooar- 
tfl of the composition of turp orring in the milky 

juice of tropical trees ; tin soluble in carbon bisul- 

phide, chloroform, ami bei Elasticity in the first is 

v combining it with sulphur, or vulcanising it. 

Bj addition of more than three per cent of sulphur, Imlia- 
ruh and hard j it is then called i 

i is used for the manufacture of surgical and various 
other articl ba is softened bj heat, and can 

iu thi be worked in 



OHAPTEH \ 

COMPOUNDS or i».. 
\ L 

574. Constitution. — A number of com] 

Btitution of which has : 

-, but which may )».• regarded a- nearly t 

f the 

Anilin, or phenylamin, lias alrea 
been • ie of the products <-f dry di 

of ind;_-<». The whole ii. 

Aorieas, i stts sob- 



348 DESCRIPTIVE CHEMISTRY. 

stance, naturally occurring, and which may be artificially 
prepared in several ways. It is a product of putrefaction 
of albuminous matter, and can be obtained by heating 
albumin with potassium hydrate. By the action of ozone, 
it is converted into indigo-blue (indigotin). 

575. Indican. — Several species of indigo-fern and a 
number of other plants contain indican, a glucoside, 
which, by being boiled with dilute acids, or by fermenta- 
tion, is broken up into sugar and indigo-blue. Indican 
may be prepared from the plants by soaking them in cold 
alcohol and evaporating the extract. Indican remains as 
a brown sirup. Indigo is prepared from the plants by 
chopping their leaves and soaking them in water for 
twelve hours or more. The liquid is then poured off, 
and with frequent stirring exposed to the air, when crude 
indigo settles as a blue powder, which requires to be 
purified. 

576. Indigo-Blue (C 8 H 5 NO), in a pure state, is a dark- 
blue, odorless, and tasteless powder, insoluble in water, 
alcohol, and ether, but soluble in chloroform, paraffin, 
phenol, and benzene. Fuming sulphuric acid dissolves it, 
forming indigo - monosulphonic and indigo - disulphonic 
acids. The potassium salt of the latter, which dissolves 
in water with a blue color, is known in commerce by the 
name of indigo - carmine. Indigo-blue, when carefully 
heated to 300°, is volatilized, forming a purple vapor, 
which condenses to dark-blue crystals of the pure sub- 
stance, having a metallic luster, also possessed by the com- 
mercial indigo. The most common process of preparing 
indigo-blue from crude indigo, much applied in dyeing, 
depends on the indigo-blue being converted into indigo- 
white (C 8 H 6 NO), by reducing agents, such as ferrous sul- 
phate, or glucose in an alkaline solution. Cloth dipped 
into an alkaline solution of indigo-white rapidly acquires 
a deep and permanent blue tint, when exposed to the oxi- 
dizing action of the air. Indigo-blue can be artificially 



(JUVosiOTR 349 

d from Beyers! sources, bat the products are 

laoe the natural indi 

tides. 

577. Diffused throughout the vegetable world then 
toe of compounds of widely varying composition, 
from nitrogen, hut all contain 
. hydrogen, and oxygen* They may all he split 
in: ad another compound arisen heated with 

dil . , <»r alkalies, ren with water. They 

undergo a similar decomposition by the action of certain 
Eermenl [uently the ferment causing this chang 

ad associated with them in the Bame plant. From the 
• bat in all these decompositions a kind <>f 
snp - formed, these bodies haye received 

tin- nam I ' I them and the products of 

their decomposition ai amorph 

have already been d< 

fol- 
low also of BCientific or practical inl 

a crystalline compound occurring in willow-bark, is split 
int in (salicylic alcohol) and sugar by the ferm< 

emulsin and diastae 

i u n. \. H f O=sO f H i O t +O i H lt O i p 

the Bweel principle of licorice-root, 
dilute acids split ii f in and 

d of dilute acid- yi.-id- the alkaloid lolanidin 

578 I • real nun 

I which 

exa mi- 

cal characters, few 



350 DESCRIPTIVE CHEMISTRY, 

or alkalies. They are not nitrogenous. Many of them 
are distinguished by strong effects on the animal system, 
and are therefore applied in medicine. Aloin is contained 
in aloes, the dried juice of the leaves of several species of 
aloe. It may be extracted by water; it crystallizes in 
slender needles, and acts as an energetic purgative. Gen- 
tianin, forming yellow needles, is extracted from the root 
of Gentiana lutea by ether, and acts as a bitter tonic. 
Lupnlin, contained in the yellow glands of hop-flowers, 
is an amorphous, yellow mass. Picrotoxin crystallizes in 
slender needles, and is extracted by alcohol from the seeds 
of Menispermum cocculus. It is a strong narcotic poison. 
Santonin, the active principle of the flowers of Artemisia 
santonica, which are known by the name of " worm- 
seed." It is extracted by boiling milk of lime and pre- 
cipitated by hydrochloric acid. It crystallizes in shining 
white prisms, turning yellow by sunlight. Cantharidin, 
though only produced in Spanish flies and several other 
insects, resembles some of the last-mentioned substances 
in properties. It crystallizes in four-sided prisms, and sub- 
limes when heated. It produces blisters on the skin, and 
acts as a strong poison when taken internally. 

§ 4. Pectous Substances. 

579. Little more is known of the constitution of these 
bodies than that they consist of carbon, hydrogen, and 
oxygen. The juices of ripe fruits, and roots such as tur- 
nips, after boiling, gelatinize. This property is due to the 
presence of pectin. Pectin may be obtained from the 
juice of ripe pears, after removing the lime by oxalic acid 
and albuminoids by tannin. On adding, alcohol, pectin 
separates from the juice as a jelly, which, when dry, forms 
an amorphous and tasteless mass. Unripe fruits do not 
contain pectin, but pectose, which, during the ripening 
process, is converted into pectin by the ferment pectase. 
This change is also rapidly effected by the action of acids. 



VBQMTABUI COLORING HATTEB ;j\i 

bring Matters. 

580. Vegetable Coloring Matters. — Various and beau- 
tiful as aiv many of the color- produced by living plants, 

comparatively tew of them outlast the lif^ o! their mother 
-ins. These fen I verj different, parti] 

doubtful constitution. Borne of them, Buoh as alizarin 
md indigo \ re not formed in Living plants, 

bat are products <»f fermentation in dead organisms. 

Many vegetable coloring-matters arc distinguished by the 

property of assuming differeni tints when broughl in oon- 

th acidfl and with bases; on this account they arc 

applied in chemistry for ascertaining the acid or basic 
[ a compound. Those which combine directly 
with vegetable and animal textures are called genuine, 
while others combine with fiber only after it ha 
im] 1 with a m<>rdant % generally an aluminum-, 

tin-, or ferric salt Oxidu • nt>, such as chlorine 

peroxidi organic i i bleach- 

also convert many of them into 

colorless compounds, some of which, however, can be re- 
averted into the original substance. W all-know d mem- 
rs of this class of i Chlorophyll the col 

; principle <»f leaves and other green organs of plants. 

Associated with wax and other SUbfltano depos- 

lis as chlorophyl-grannles. It is believed 

gist of , :•, tlie lal 

foliage assume^ red low 

tints. The various 'jv tracted from pi.. 

by alcohol, chlorophyl in a d 

less impure and changed state ; water docs notdissohe 

it. It ably slso ir<m. I 

■ How <■■ 
in • 

-lor. 'I 

icid, with ti that paper, tl 



352 DESCRIPTIVE CHEMISTRY. 

and dried does not become yellow again on adding acids. 
Litmus, a blue dye-stuff, is believed to be a product of the 
oxidation of orcin, a dihydric phenol occurring in several 
lichens. Litmus paper, prepared by steeping filter-paper 
in an aqueous extract of litmus and drying, is the most 
common means of the chemist for testing the acid, or 
alkaline character of a liquid. Acid solutions turn the 
blue color of litmus to red. Alkaline liquids turn the red 
back to blue. 

581. Coloring-Matters of Animal Origin. — The animal 
world, and especially insects, yield a variety of dye-stuffs. 
Carminic Acid (C I? H 18 O 10 ) occurs in certain plants and 
in cochineal, which consists of the dried females of Coc- 
cus cacti. Carminic acid is a red, amorphous mass, easily 
dissolved by water and alcohol. Its chemical character 
is that of a glucoside, being decomposed by dilute acids 
into carmine red and a kind of sugar. Commercial car- 
mine is a combination of carminic acid and alumina ob- 
tained by precipitating an aqueous extract of cochineal by 
alum. It is insoluble in water, but dissolves freely in am- 
monia and alkalies, such solutions being applied as red 
ink. Purple, a dye-stuff formerly much produced in the 
Orient, is prepared from the yellow secretion of the purple 
snail, which, on exposure to light, assumes a scarlet or 
purple color. Hwmatin is the compound which imparts 
the red color to blood. It is obtained by the action of 
alcohol and dilute acids on oxyhemoglobin as a dark-blue 
powder, which dissolves in alkalies with a red color. It 
contains nitrogen and nine per cent of iron. Hcemin, or 
haematin-hydrochlorate, may serve for the detection of even 
minute traces of blood. 

§ 6. Alkaloids. 

582. Many plants are known to produce powerful 
effects on the animal system when taken internally, or ap- 
plied externally to a sensitive part of the body. In most 



ALKALOIDa 

of them peculiar const ituenta haw been discovered, which, 
when separated in s piu . exhibit i pronounced alka- 

ehara- I ':i this account they were named AVoOr 

- >. They all contain nitrogen, 

••on, and hydrogen, most of them also nx\ The 

former are liquid, volatile, and strong-scented, the latter 

In many respects they resemble the 

ited ami: . <t amines, and arc believed t<» ha\c 

milar constitution, although attempt.- to prepare them 
artificially have met with lit 1 1 . s, and snalysifl has 

ly imperfectly n n>it ut i« »n. Many have 

1 as derivatives <>f pjjridtfU and quinoli 
known * irlv related to urea. In plai 

the, lly occur combined with organic acids. 

583. Alkaloids free from Oxygen.— Time members of 
this group are well known: \ ontained in the 
seeds and leaves of tobacco, in dried leaves to the am. .nut 
of from two to eight per cent, The narcotic and nan 
ati: unoking and chewii oo f^r the d 
part is due to this ingredient Nicotine 

liquid, becoming brown by accession of air, having i itu- 

baoco-like smell, and acting ss a strong poison. 

from the seeds or leaves oi hemlook, 

a colorless, punj rtremely poisonous liquid, quickly 

n and inactive by the accession «»f air. 

Sp< 'l-tituent <»f common broom, baring oar 

fects. Its sulphate is osed in medicine. 

584. Alkaloids containing Oxygen. tried 
milky lie half-ripe capsulei <>f poppy, among other 

. alkaloids, united s ith 
mc< ilphuric ' B . \ ( I II 

hief uar lien! <»f opium. It crystallises 

in small white pri from m 

oluble in potassium 
sodium hyd- ition. l\< j.ren noe is recognized bj 

blue color which it imparti to itioD *»f (erricchlo- 



354 DESCRIPTIVE CHEMISTRY. 

ride. It reduces iodic acid, setting iodine free. The 
value of opium as a medicine depends chiefly on the 
quantity of morphine which it contains, and which should 
amount to at least ten per cent. The hydrochlorate and 
sulphate are the most common in medical use. Codeine 
(C 18 H 21 N0 3 ,H 2 0) or methyl morphine, is a homologue of 
morphine, and may be obtained from it by heating it with 
methyl iodide. It is also found in opium. Narcotine 
(C 19 H 14 (CH 3 ) 3 N0 7 ) was the first base separated from opium, 
but it was considered as a salt, while in morphine the 
basic character was recognized at once. 

585. Cinchona Alkaloids. — The bark of the cinchona- 
tree contains several alkaloids combined with quinic and 
cinchona-tannic acids. The home of this tree is in the 
forests of the Andes, and it is cultivated in the East Indies 
and Java. These alkaloids, on account of their fever-allay- 
ing and strengthening properties, are valuable medicines. 
The four most important ones are quinine, C^H^NaC);,, 
cinchonine, C 19 H 22 N 2 0, quinidine, which is isomeric with 
quinine, and cinchonidine, which is isomeric with cincho- 
nine. Quinine and quinidine, occurring more abundantly 
in the bark of the stem than the other two, which pre- 
dominate in the bark of the branches, are believed to 
originate from the latter by oxidation. 

586. Strychnos Alkaloids. — Some trees belonging to the 
genus Strychnos, and growing in the East Indies and South 
America, are noted for the extremely poisonous properties 
of their seeds and other parts. This effect is due to the 
presence of several alkaloids. They are generally obtained 
from the seeds of Nux vomica (crow- figs). It is to Strych- 
nine (C 21 H 22 N 2 2 ) that they chiefly owe their poisonous 
action. Cold water dissolves only -^-q of its weight of 
strychnine, but it is more readily soluble in essential oils 
and chloroform. Prom its solutions it crystallizes in small 
brilliant octahedrons, of exceedingly bitter taste. Such is 
its intense bitterness, that it imparts it perceptibly to 



ALKALOIDa 

,000 times its weight oi deadly poison, 

g»5 of a grain killing a dog in thirty seeonds. It t. 

t upon the nerve-centers of the spinal axis, producing 

'ill convulsi- 

The terrible wouraii poison, with which the Smith 
American natives poison their arrows, and which u some- 

time8 used as a remedy tor i, appeal main a 

principle nearly allied if noi identical with strychnine. 

an alkaloid closely allied to strychnine, and 

obtained from the same genus of plants. 

587. Alkaloids of the Solanacese.— The family of the 

ii distinguished by the poison- 
of nmst of its members. It has already 

D mentioned that many parts of the potato-plant emi- 
D Bolanil and thai nicotine is a constituent of 

tobacco. In three other well-known members of the fam- 
ily, '/"■ -'7>/>/>\ and black / 
thr alkaloids are bond, exhibiting the same 

arnica! r - and the nuns physiological effects. 

Th , and >ometimes death. When. 

f them ia breoghi into the • tnsider- 

able enlargement <>f the pnj.il is produeed, lasting for 

ira These alkaloids are Atropine^ ffysecyaatina, and 

une isomeric, and sgree in most of their 

The two Brst named i and 

M, hut <litTer in strueture somewhat ; hyo- 

ami brown. The plant- from which they 

are prepare n found to contain original!] only 

hyoaoyamine, winch, during the process of e\ 

• forms. I [enoe the] d 

all 1m- regarded efl D alkaloid q| the • 

mul 

588. Alkaloids of other Plants. Ukaloid nmd 
in m.inv other plant-, a: in faun lies are < 1 1 - T i ? 1 ^r 1 1 i - ! 

by the greaJ ies of thy kind which tb 

ducc. ( flon 



356 DESCRIPTIVE CHEMISTRY. 

coca, has recently become famous as an angesthetic. Theo- 
bromine, Caffeine (theine), the former a constituent of 
cacao-beans, the latter of coffee-beans and leaves of tea, 
were classed among alkaloids, but from their products of 
decomposition they appear to be substituted carbamides. 

The stimulating effect of coffee and tea is in part due 
to the presence of caffeine compounds. Coffee seldom 
contains more than 1*5 per cent of the principle, while 
tea furnishes three or four. Caffeine crystallizes in long, 
flexible, silky needles, has a slightly bitter taste, and dis- 
solves sparingly in cold water, but freely in hot water. 
The effects of coffee and tea are, however, not due to the 
caffeine alone, but are modified by various other ingredi- 
ents. In tea, the alkaloid is associated principally with 
tannin and an essential oil ; in coffee, with empyreumatic 
and essential oils. Both compounds are weak bases, their 
salts even by boiling water being split up into acid and 
base. 

§ 7. Nitrogenous Animal Snbsta?ices. 

589. Animal Compounds of Basic Character. — In the 

normal as well as in the diseased animal system compounds 
of basic character are produced, in several respects similar 
to alkaloids. Creatine (C 4 H 9 N 3 2 ), a permanent ingredient 
of the muscular juice of higher animals, is extracted from 
chopped raw meat. Creatine crystallizes in shining prisms, 
and is sparingly soluble in water. It has basic properties. 
On boiling with barium hydrate it yields urea. It is to a 
considerable amount contained in extract of meat, the 
animating effect of which is believed to be for the greatest 
part due to this ingredient. Boiling with dilute acids con- 
verts it into creatinine (C 4 H 7 N~ 3 0). Its reaction is a feebly 
alkaline one, though it behaves as a strong base, setting 
free ammonia from its compounds. By heating with al- 
kali, it is converted into creatine. 

590. Gelatinous Substances. — Various parts of animal 
bodies, such as skin, connective tissue, and tendons, con- 



MIL S VMM \l -I RST VN 

tain , which may be i utinued boiling 

of ' irts with water. The solution, upon ooolii , 

nt jelly. Bj drj 
a brittle residue is obtained, which, if impure and 

the purer and colorless produ 
; by the nan Latin and at 

: industrial purpo>r>. lilu< rally manufactured 

aides, which arc steeped in 

lime-water to remove hair, blood, and other import 
Saving to the air for Borne da] b, to oon- 

ime into carbonate and thua to prevent 

I on the material, they are boiled 

until a sample of the solution gelatiniiefl on 

Impurities havinir heen allowed to Bettle, the 

liquid Le ; into flat wooden dishes, where it Bolidi- 

i mass > 'in into oed 

1 dr\ inir proce-s iv- 
quirefl a medium I the air fre- 
quently causes putrefaction and i -. A' 

pure variety of glue prepared from the swimming-bladder 
of • in may also be obtained from boi 

by with weak hydrochlori . which 

cium phosphates and other ingredient -. 
itin as a *<> the 

which the bone had. Gelatin 
hy< 'i, the latter to the amount 

I latin is not dissolved I 
water, alcol ids, bu1 let on- 

I dissolve it. forming tion known 

as liqui Tannic acid, even in rery dil 

iroducea s yello* 
putrefaction 

591 Proteida, or Albuminoids 
II as the tissues of th«- various 
cot j, partly in a sol 

nu: u oomg 



358 DESCRIPTIVE CHEMISTRY. 

composition, but of differing properties. They also abound 
in blood and in most animal juices and secretions. From 
the best known of them — albumen — they received the 
name of albuminoids ; formerly believed to originate from 
one compound — protein — they were also called proteids. 
They occur in all plants, and it is exclusively in vegetable 
organisms that they are formed ; but being taken up by 
vegetable-feeding animals, they pass into their bodies and 
are converted into substances of the highest vital impor- 
tance. Their empirical composition is C 7 2H 112 N 18 22 S, the 
proportion of nitrogen amounting to fifteen or eighteen per 
cent. Their chemical structure has not yet been definitely 
ascertained, but it is assumed to be analogous to that of 
urea. The value of human and animal foods for the most 
part depends on the percentage of albuminoids they contain. 
Among vegetable products, peas, beans, and the cereals 
are the richest in proteids ; they are, therefore, considered 
as the most nourishing vegetable food. Proteids occur in 
three different natural states. They are either dissolved in 
vegetable or animal juices, or transformed into organized 
parts of tissue, or deposited as solid amorphous secretions. 
When kept in a moist state they soon putrefy, yielding a 
large number of products, among which are ammonia and 
sulphureted hydrogen. In contact with the juices of the 
stomach, all proteids are converted into soluble peptones. 
These bodies are distinguished from dissolved proteids by 
their ability to pass through animal membranes, the as- 
similation of albuminous food chiefly depending on this 
circumstance. Proteids are also dissolved by alkaline 
liquids, the dissolved matter being precipitated again by 
the addition of an acid. Albuminoids are also precipitated 
by tannic acid and by many metallic salts ; on this account 
they are frequently applied as antidotes against the effects 
of poisonous metals. Albuminoids may be classed in four 
groups : 1. Albumens and globulins ; 2. Fibrins ; 3. Caseins ; 
4. Albuminoids exhibiting specific properties and reactions. 



VLIil'Ml \ WI> ULOUULDH 

592. Albumens and Globulins. -They are precipitated 
by applying heat /' i is the chief constituent 
of the whito of birds 1 eggs, which, on evaporation at a 
Ion ratnre, leaves it aa ■ translucent, amorph< 

due, soluble in water. It ooagolatee at 70 (. > mt- 
a the moel abundant albomin id in animal 

juices ami identical with the albumon dissolved in the 
juices of plants, which is se p a ra ted by heat, forming 
loam on the surface of the juice Blood, when left to 
id for some hours, separates into two layers; a sedi- 
ment containing the red corpuscles, and ■ yellowish 
liquid, the scrum, from which, by evaporation, albumen 
may be obtained. It ooagnlates at aboal the Bametem- 
iture as egg-alhumen. Globulin* differ bora album* 
'heir insolubility in pure p iiiL r , however, dis- 

soh lute solutions of common salt 8erum-g 

Coagulating at about I ., is found associated with alhu- 

meo in blood-serum and in other animal juices. Mf( 

•hicf liquid constituent of contractile muscular 

p; it is also called the 

tsma, and solidifies 

after the death of the ani- 

ising the 

hardening of the flash* 

beat it is changed into 

coagulated albumen. The F „.. m 

solid substi ititut- 

_' muscles is railed mUBCUlin, It 0CCUTI in bundles, as 

shown in I minklei 

■-markings. If i piece of lean beef is washed in clean 

its red color, which is due to blood, gradually d 
:^ars, leaving a whitish mass c om posed of musoulin, 

and the areolar tissue which bin the mo 

together. lak- i sapable of b ted 

insoluble body. 

593. Fibrin. A lew mii awn 




360 DESCRIPTIVE CHEMISTRY. 

from the veins, a portion of it solidifies, forming what is 
known as the clot. This solid part consists almost en- 
tirely of fibrin, and represents the proteid constituent 
of the blood. It differs from most proteids in being 
nearly insoluble in water, and alone possesses the prop- 
erty of spontaneous coagulation. Its proportion varies 
in the blood, being increased in inflammatory diseases 
and decreased in anaemic diseases, such as typhus and 
chlorosis. When purified by washing, it is a white, amor- 
phous, elastic mass, which is made hard and brittle by 
heat. 

594. Vegetable Fibrin or Gluten. — When wheat, rye, 
or barley flour is kneaded in a bag, or on a sieve with 
water, the soluble ingredients and starch are washed away, 
and a tough, viscous matter (gluten) remains, which be- 
comes a horny, brittle mass by drying. It is similar to 
animal fibrin both in physical and chemical character, and 
is supposed to consist of several proteids. Gluten is very 
liable to decompose, and in this state is capable of induc- 
ing fermentation. In germinating grain, gluten is trans- 
formed into diastase, the ferment which in the brewing 
process converts starch into dextrin and sugar (532). In 
bread-making the decomposition of gluten is also frequent- 
ly utilized. A dough made of flour and water is left in a 
warm place, until chemical change, manifested by ris- 
ing, has set in. The " leaven " thus produced contains a 
chemical, unorganized ferment, which, when added to a 
dough of water and flour, induces fermentation in the 
sugar of the flour, breaking it up into alcohol and carbon 
dioxide. It is the presence of the latter gas which causes 
the bread to rise. 

595. Casein is an essential albuminoid of milk, exist- 
ing in it to the extent of about three per cent, and 
forming its curd, or cheesy principle. In milk it is held 
in solution by the presence of a small portion of free 
alkali, and, when this is neutralized by an acid, the case- 



881 

he milk 

Almos . 
albuminoid clo» 
resi 

liable by heat, bul 
julated I ni- 

The Ch -in 

peas, which ;' milk- 

manufacturi 

casein, bul rennet, the mucous membi 

:i of which, warmed wil 
of milk. ient Fresh I so 

thai which has undergone a slighl I 

•n- 
rticular fermeni contaii 

596. Milk from the 

that it constitul the 

og animal I ently must 

sarj for the rapid develop- 

I • . • - ntiallv 

: : the pn !i;it 

ined under a mi 

Quid, in which fj 

nf 

i if the in thus 

the 

dumb, fori i milk, wheu perfectly 

fit* bly alkaline . 

aci«l. I 

LI 



362 DESCRIPTIVE CHEMISTRY. 

below a statement of the composition of cow's milk, from 
an analysis made by Haidlen : 

Water 873-00 

Butter 3000 

Casein 48'20 

Milk-sugar 43*90 

Calcium phosphate 2-31 

Magnesium phosphate 042 

Iron phosphate 0-07 

Potassium chloride 1*44 

Sodium chloride 0*24 

Soda combined with casein 0*42 

1000-00 

Milk, when taken as food, is always at first coagulated 
in the stomach, casein separating from its solution. This 
is probably due to a rennet-like ferment present, but is 
also often ascribed to the free hydrochloric acid contained 
in gastric juice. Later on the digestive action of pepsin 
sets in, dissolving casein, as it does all other albuminoids, 
and converting it into peptone. 

597. Albuminoids exhibiting Specific Properties and 
Reactions. — The red color of the innumerable globules in 
the blood of back-boned animals is due to hwmoglobin, 
a compound which, besides the constituents common to 
albuminoids, contains 0*42 per cent of iron. It may be 
obtained in microscopic crystals of various forms by mix- 
ing defibrinated blood with water and adding alcohol, or 
by evaporating the dilute solution at a low temperature. 
The blood of most animals yields prismatic crystals of 
similar structure, but the blood-crystals of some of them 
are of particular forms : those of the squirrel are hexagonal 
plates, those of the Guinea-pig tetrahedra. Haemoglobin 
is distinguished by a great capacity for absorbing gases. 
The bright-red color of arterial blood is due to the oxygen 
absorbed ; the dark venous blood contains little or none. 

598. Pepsin, Pancreatin, and Peptone. — All albuminoids 



B0BN1 3UB81 LN< 

. in panning through the alimentary canal 
are mainly by the 

articular glands of the stomach. 

obtained from the 

im; maohs. It is often admin- 

licinall] li acta only in 

in_r albuminoids into pep- 
88, whicli pass into the circulation, where thi \ arc 

aga : into j ■ ontributing to the renewal 

(tasted muscular and other I That pari of albu- 

minous food which a by pepsin Lb pepton- 

retion of the pancri 
the small intestines. The chief character- 
shing them from albuminoid 
ir diffusibility through animal membranes. The] 
in all proportions, and their Boluti< 
arc* by heat, nor are they precipitated by 

•' those Is which precipitate albuminoi 

Tie 

other j >hiiiT - upon albuminoids, and 

tssed among the 
599. Horny substances. II air, and 

ry nearly related to albuminoid 

r amoui dphur. \\ 

■••>- ively with boilin. . alcohol, 

dilute a .. which 

Jkaline 
; has the structure 

Of ! 1. 

COO. Product* of Muscular Decay The 
volvcs a contini 

of 

blood of these 

taken u] . the 0( 

I 
bio uste 



364 DESCRIPTIVE CHEMISTRY. 

products. One of them is Uric Acid, abundant in guano, 
and excreted in small amount by carnivorous animals. In 
certain diseases, such as gout, its quantity is considerably 
increased, and its solubility being very small, it is deposited 
in the joints, causing severe pains. Lithium urate is the 
most soluble of its salts, and lithium carbonate, on this 
account, is an esteemed remedy in those diseases. 

Ptomaines. — The process of putrefaction of albumi- 
noids produces compounds of decidedly poisonous charac- 
ter, which in their chemical nature very much resemble 
vegetable alkaloids. The injurious effect of rotten meat, 
cheese, etc., has in most cases to be ascribed to their pres- 
ence. They were at first discovered in corpses, and are 
also believed to originate in infectious diseases produced 
by micro-organisms (bacteria). One of them, muscarin, 
is identical with the poisonous principle of Agaricus mus- 
carines, a kind of mushroom „ 



APPENDIX. 



of />■;/>'.>.< cm thi c> rUigradi and 
hi it Tfu rmorm I 





1. 




r. 






C. 


1 


♦ 100 = 




M = + 






M-9 


_ | 




M - 












T 
















8 = 




97 = 


•J...-.Y, 




141*8 






9 = 


16-8 


96 = 




60 = 












M = 




59 = 




24 = 




11 




94 = 








23 = 






LO i 


98 = 


1994 










18 = 




98 = 








21 = 


m - 






91 = 










.;> 






















m a 
















^ 














1 














19 = 




86 = 










08 


20 = 


1 






















48 = 


























9-4 








in - 










81 = 












2ft = 




80 = 




44 = 


1 1 1 J 


9 = 








19 = 




48 = 




- 




n 












T 




•> 


l-l 










6 = 








76 = 






104 


5 = 


u 


80 = 








89 = 




4 = 


H | 


















82 = 












2 = 




8H 






1616 


86 = 










Wi 






■ 




















- 1 




86 = 




• a 




88 = 












18 = 








8 = 












81 = 




4 = 




89 = 




66 a 




80 = 


81 



























1 
frrm the number of degrees, and multi: f f. 

ide Dtgr<> 
numb e.« bj } (or 1*8), and idd 



366 



APPENDIX. 



Alphabetical List of the Elements. 

The recognized elements now number seventy-one, as given in the fol- 
lowing table, with their symbols and atomic weights. The names of the 
rarer elements are printed in italics : 

Aluminum Al 

Antimony Sb 

Arsenic As 

Barium Ba 

Beryllium Be 

Bismuth Bi 

Boron B 

Bromine Br 

Cadmium Cd 

Ccesium Cs 

Calcium Ca 

Carbon C 

Cerium Ce 

Chlorine CI 

Chromium Cr 

Cobalt Co 

Copper Cu 

Decipium Dp 

Didymium Di 

Erbium Er 

Fluorine F 

Gallium Ga 

Germanium Ge 

Gold Au 

Hydrogen H 

Indium In 

Iodine I 

Iridium Ir 

Iron Fe 

Lanthanum La 

Lead Pb 

Lithium Li 

Magnesium Mg 

Manganese Mn 

Mercury Hg 

Molybdenum . . Mo 



275 


Nickel 


Ni 


58-6 


122-0 


Niobium 


Nb 


94-0 


75-0 


Nitrogen 


N 


14-0 


137-0 


Norwegium 


Ng 


214-0 


9-4 


Osmium 


Os 


198-6 


208*2 


Oxygen 


O 


16-0 


11-0 


Palladium. 


Pd 


106-5 


80-0 


Phosphorus 


P 


31-0 


112-0 


Platinum 


Pt 


197*4 


133-0 


Potassium 


.... K 


39-0 


40*0 


Rhodium 


Rh 


104-0 


12-0 


Rubidium 


Rb 


85-3 


140*5 


Ruthenium 


Ru 


104-4 


35-5 


Samarium 


Sm 


150-0 


52*1 


Scandium 


Sc 


440 


58-6 


Selenium 


Se 


79-0 


63*5 


Silicon 


Si 


28-2 


159-0 


Silver 


.... Ag 


108-0 


1460 


Sodium 


.... Na 


23*0 


1659 


Strontium 


Sr 


87*5 


19*0 


Sulphur 


S 


32-0 


69*5 


Tantalum 


..... Ta 


182-0 


72-0 


Tellurium 


Te 


128-0 


196-7 


Terbium 


Tr 


148-8 


1-0 


Thallium 


Tl 


204-0 


113-4 


Thorium 


Th 


231*4 


127*0 


Tin 


Sn 


118-0 


198-0 


Titanium 


Ti 


48-0 


560 


Tungsten 


W 


184-0 


138-5 


Uranium 


U 


238-5 


207-0 


Vanadium 


Y 


ol'3 


7-0 


Ytterbium 


.... Yb 


172*8 


24-0 


Yttrium 


Y 


89-8 


55-0 


Zinc 


Zn 


65-3 


200*0 


Zirconium ...... 


Zr 


90*0 


96-0 









\rn\i»i\ 



867 



1 f s II I ' ■ 



I I H 




. . = 




, . = 




Decwnotrr = 




Metsu . . . = 


l 


Decimeter = 


0*1 • 


. i.. = 


o-oi 


Millinunr (mm. i . = 


|] u 






. . . = 


1000 grams, 


. . - 




: 


10 


QftAM . . = 


l 


Decigram = 


.'•i 


• 


l M 


m = 


M-,,,,1 - 



= 1000 ! 



iter. . 
Milliliter.. 



10 

1 liter. 

Ml • 

1 M 

O-Ool" 



l liter 

o .... = 15' i 






I : «in. 

avoir.. arms. 



I /V<y<,- \ 



a-cet'-y lene. 

al-1- 

iiin-um. 

- 
an -ii-fn. 

a-toi 1 1 



A-Vn 

'•■Mill. 

Berth 

i 
i 

a). 

lit. 



368 



APPENDIX. 



di-a-ther'-man-cy. 

dif-fu'-sate. 

Dumas (Du-mah'). 

Durkheim (Door' -kime). 

eb'-ul-li'-tion. 

e-lec-trol'-y-sis. 

er-e-ma-cau'-sis. 

eth'-yl. 

eth'-yl- ene. 

Fahrenheit (Far' -en-hite). 

flu'-o-rine. 

Fraunhofer (Frown -lio-fer). 

Galvani (Gal-vaK -nee). 

Gay-Lussac ( Gah! -ce-lm -sac). 

Gerhard t (Gair' -hart). 

glyc'-e-rm. 

gly '-co-gen. 

go-ni-om'-e-ter. 

hae-mo-glo'-bin. 

ha'-loid. 

Hauy (Ah'-u-y). 

hep'-tad. 

hip-pu'-ric. 

hy-drox'-yl. 

i'-o-dme. 

i-som'-er-ides. 

i-som'-er-ism. 

i-so-mor'-phism. 

Joule (Jole). 

Kirchhoff (Keerk' -hoff). 

Klaproth (K lap' -rote). 

laev'-u-lose. 

Leyden (Li' -den). 

Liebig (Lee' -big). 

lith'-arge. 

lith'-i-um. 

Mayer (Mxf -er). 

mer-cu'-ric. 

mer-cu'-rous. 

met-ath'-e-sis. 

meth'-yl. 

inet'-ric. 

mol'-e-cule. 

mon'-ad. 

mor'-phine. 

mol-yb-de'-num. 



nas'-cent. 

nic'-o-tme. 

ni-trog'-e-nous (ni-troj -e-nus). 

6 le-fl-ant. 

ox'-ide. 

o'-zone. 

par'-af-fin. 

per'-is-sad. 

phe'-nyl. 

phlogiston (Jlo-jis' -toil). 

phos-phor'-ic. 

pho'-to-sphere. 

Pictet (Pic-tay). 

plat-in'-ic. 

plat'-i-num. 

py-ri'-tes. 

pyr-o-gal'-lic. 

quan-tiv'-a-lence. 

quinine [kwi'-riine, or kivin'-ine). 

Reaumur (Ray' -o-miir). 

saccharin (sak'-a-rin). 

sa-li-cyl'-ic. 

sa-li'-va. 

Scheele (Shay -lay). 

Schonbein (Shane' -bine). 

Seidlitz (Sid'-lits). 

se-le'-ni-um. 

sil-ic'-ic. 

sil'-ic-on. 

spec'-tro-scope. 

spiegeleisen (spe -gel-i-sai). 

sta-lac'-tite. 

sta-lag'-mite. 

ste'-ar-me. 

strychnin (strik '-nin). 

suc-cin'-ic. 

sul-phu'-ric. 

sul'-phur-ous. 

tar-tar'-ic. 

tet'-rad. 

the'-ine. 

ther-mot'-ic. 

tourmaline (toor ~ma-lin). 

u-niv'-a-lent. 

u'-re-a. 






QU ESTION S 



[NTRODUCTION. 



iiy the terms phenomena and order of nature f 
phenomena of nature, i. \N hnt 
are phyi I chemleaJ changes. 

6. Art 

CHAPTBfi I 

7. D \Vh;it is a 

body? A rolnme, mass, and density. 10, Show 

; to the chem- 

12. Wl: D • till' 

balance. 11 

BOH 

-<■•? IT. 

the unit uf the French 
Bon may density be ratfmatnd f 

OHAPTEB I L Q r a 

28. Wii \: • in<v If ill.- D 

Ifl and li'j 

of 
I be 
taken in finding the sp 

the ipecific i-ri\it j of soluble solids !>'• obtained 1 29 Hon ma] the 
specific gravity of liqo] 
the | 
specific gravity afford means of identifying bodies? 



370 QUESTIONS. 



CHAPTER III.— Molecular Action. 

33. What reason can be given for the conclusion that matter is uni- 
versally porous? 34. What are molecules? 35. State what you can 
of the divisibility of matter. 36. Describe the motions of molecules. 
37. Give distinction between adhesion and cohesion. 38. What is cap- 
illary attraction ? 39. How may a gas be driven out from a solution ? 
40. How do insects walk upon water? 41. Explain what takes place 
in diffusion. 42. What principle explains the stability of our atmos- 
phere? 43. Give illustrations of diffusion through porous partitions. 
44. What occurs in atmospheric respiration ? 45. What are crystalloids 
and colloids ? 46. What is meant by the terms solution and solvent ? 
47. What conditions favor solution ? 48. When is a liquid saturated ? 
49. How may solids be separated from solution ? 50. What is a pre- 
cipitate? 61. What is occlusion ? 52. What are crystals? 53. What 
are substances called which do not crystallize ? 54. How may crystals be 
artificially produced? 55. What is mother-liquor ? 56. What is said of 
crystals by fusion ? 57. Does crystallization ever take place except in 
liquids? 58. What is annealing? 59. State phenomena attending crys- 
tallization. 60. Give some conditions of the growth of crystals. 61. 
What forms do liquids tend to assume on crystallizing ? 62. What are 
primary forms? 63. How many systems of crystallization are there? 
64. What example of the derivation of form is given? 65. What is iso- 
morphism ? 66. What is dimorphism ? 

CHAPTER IV— Heat and Chemical Change. 

67. Give the term which is applied to the science of heat. 68. What 
is the general effect of heat upon matter ? 69. How may the cohesion 
of a solid be overcome ? 70. May gases be expanded indenifitely ? 71. 
What do thermometers measure ? 72. What advantages has mercury as 
a thermometric fluid ? 73. Give the different thermometers in use, and 
state the peculiarity of each. 74. What is the melting-point of a sub- 
stance? 75. Give the distinction between latent heat and sensible heat. 
76. What is specific heat ? 77. Explain how freezing is a warming pro- 
cess. 78. What is a freezing mixture ? 79. Explain the process called 
boiling. 80. What circumstances affect the boiling-point ? 81. What 
are substances called that vaporize readily? 82. What becomes of the 
heat which has been consumed in converting liquids Into vapors ? 83. 
On reversing the process, what occurs ? 84. What use is made of this 
phenomenon? 85. What is the effect of evaporation ? 86. Explain the 
cryophorus. 87. What is the dew-point ? 88. Explain the hygrometer. 
89. What relation is there between the vapor from a cubic inch of water, 



QUESTIONS :;;i 

Ml Wl 
91. l tin tenni 

t<» tlir liquid or H>lid sU 
which led kQ the in w t li 

ri i- mimimed t.. i>.- in, 
the mold .<<* \\ | Mt j„ t |„. 

lilAlMKI 
I 

- 

cuit be it I .« in. 

creased • *' . with stee edf L06 !'■ 

I laieD'i battery. l< Icitj 

- win; ii I ft \v;. : . h bodiei u 

elect ro-ncgative, which 

CHAFTEB vi -1 iocai Ob 

ill. 

I the 

spectrum ? 

pU<-. die 

day and year? lift. which Is most actire in y< 

OHAPTKfl TD 

I is spectrum a 
119. 

red rays* 
ieeooqweedf 121 Wh.it i- Mid of the spectrum of the electric light ? 

ttnes ? 1 



372 QUESTIONS. 

bright lines produced by burning terrestrial substances ? 131. What are 
absorption-lines ? 132. What kind of light do vapors absorb ? 133. What 
clew is given us by Fraunhofer's lines? 134. Give illustrations showing 
the delicacy of spectrum analysis. 135. Mention the names of the new 
elements discovered by this means. 136. Explain the use of the spec- 
troscope in steel-making. 137. Is the spectroscope used in testing organic 
substances ? 138. What elements are found in the sun ? 139. What 
evidence does spectrum analysis give us that stars are suns ? 

CHAPTER VIII. — General Character of Chemical Action. 

140. State the difference between elements and compounds. 141. De- 
fine analysis, proximate, ultimate, qualitative, and quantitative. 142. Give 
a general idea of chemical force. 143. How do the effects of chemical 
force differ from those of the physical forces ? 144. How is chemical 
action affected by cohesion, heat, light, and electricity ? 145. What is 
catalysis ? 146. When will nitrogen and hydrogen unite to form ammo- 
nia? 147. Is there any variation in the intensity of chemical action? 
148. Has chemistry any relation to mathematics ? 149. Give the prin- 
ciple underlying the law of definite proportions. 150. Explain the law of 
multiple proportions. 151. Give an example of equivalent proportions. 

CHAPTER IX. —Theoretical Chemistry. 

152. Give an idea of the old atomic theory, and that of Dr. Dal ton. 
153. Define the term molecule as used by the physicist. 154. As used by 
the chemist. 155. What is the ultimate unit of the chemist called ? 156. 
What quantity of an element does the symbol represent? 157. What 
theory was first given in explanation of chemical changes ? 158. What 
was meant by phlogiston ? 159. Give a general idea of the binary theory. 
160. What theory was the outgrowth of the binary theory ? 161. Give 
a statement of the theory of types. 162. Do substitutions take place, 
atom for atom? 163. Define the term atomicity, and give groupings 
illustrating the subject. 164. What is quantivalence ? How is it ex- 
pressed? 165. What is the significance of bonds? 166. What relation 
exists between the number of bonds and the ability of the atoms to 
combine with each other? 167. Define the terms perissad and artiad. 
168. May a perissad ever become an artiad ? 169. How is it supposed 
that changes of quantivalence maybe explained? 170. When may an 
atom or molecule exist free ? 171. Does the quantivalence of a molecule 
depend upon the atomicity of its elements ? 172. How may molecular 
chains be formed? 173. What are radicals? 174. Define compound 
radicals? 175. Can compound radicals exist free ? 176. On what the- 



QUESTIONS 
I. 

• Hon aiv thfl tWO kdfl 

tu eawnliil constituent i.f ;.:-.!>. ims, and salts? L8& What deter- 
mines the beai - • w ii.it 

■ 
an- lee? 189 

ison 

a- having dimensions ? 1 '.»•".. What is tin- Ian ol Arogadro? 197. What 
com bed regard gaseous tn< 

1 aeriform bodies n 

W]:.it 

lo gases o 

< H \ 
202. leeem ha\ 

System. 206. Give son, 

- of 
substances. 208. What si 

OHAFTEB \i -Tb On m 

" 

i v 
named? 

groups separar a? 22ft. In what 

form may ohemJca] reactions be expressed? 



374 QUESTIONS. 

CHAPTER XII.— Hydrogen. 

226. What are the quantivalence and atomic weight of hydrogen ? 
22*7. What is the significance of the term hydrogen ? 228. To what ex- 
tent is hydrogen found in nature ? 229. In what different ways may 
hydrogen gas be obtained ? 230. Describe a pneumatic trough. 231. Give 
the physical properties of hydrogen. 232. How does hydrogen compare 
with other elements in weight ? 233. What is known of its inflamma- 
bility and explosiveness ? 234. How may hydrogen be ignited without 
the application of heat? 235. What is occlusion? 

CHAPTER XIII.— The Halogens. 

236. What is the general character of the halogens ? 237. Is fluor- 
ine found uncombined in nature ? 238. What is the distinguishing char- 
acteristic of hydrofluorine acid ? 239. Where is chlorine chiefly found ? 
240. How is the gas obtained ? 241. What are the properties of chlorine ? 
242. Its uses ? 243. How does chlorine act as a bleaching agent ? 
244. What is the composition of hydrochloric acid? 245. Give the 
reaction which takes place when sulphuric acid acts on sodium chlorine. 
246. Plow may chlorine combine with oxygen ? 247. What use is made 
of chlorine monoxide ? 248. What are the properties of chloric acid ? 
249. How is bromine obtained ? 250. Give properties and uses of 
bromine. 251. What compounds does bromine form? 252. What does 
the term iodine refer to ? 253. What is the test for iodine ? 254. For 
what is iodine used ? 255. What are the iodides, and for what are they 
used? 

CHAPTER XIV.— Nitrogen, Phosphorus, Arsenic, Antimony, Boron. 

256. How is nitrogen obtained ? 257. For what is nitrogen remark- 
able ? 258. Give the composition and method of obtaining ammonia. 
259. What are its properties ? 260. Why was it called spirits of harts- 
horn ? 261. Describe the use of Woulfe's bottles. 262. What are the 
uses of ammonia ? 263. What is ammonium ? 264. When hydrochloric 
acid and ammonia are brought together, what substance is formed ? 265. 
Give the equation which expresses the reaction when ammonium chloride 
is formed. 266. Nitrogen combines with oxygen forming what com- 
pounds ? 267. What is laughing-gas ? 268. What effect is produced on 
the nervous system by nitrogen monoxide ? 269. Give composition of 
nitric acid. 270. Its properties and uses. 271. Describe aqua regia. 
272. What are the sources of phosphorus in nature? 273. What is 
the molecular symbol of ordinary phosphorus ? 274. How is it obtained? 



Ql ESTIONS 

rtirs of this clement, l! 
be < whel ii »' ■■• 

181, Dei 

test. be distill 

Wli.it 08M I 

GHAFTBB \ '■ 

295. 

stances can o\ 
■ 

or a stci ■'. bora with brill 

Ho* ! i"u i- none «li 

•ay • 

808. What i- laid <»t' the meqnal expansion of water? BIO. \m there 
any relation existing bit 811. 

it can be said of the MftfOOl 

t 

In surface vaj 

are found in Mft-wal i 

may wat.r be 18 Gi?e the rhenilrel properties of inter, 

!, of 

t o the conclu - -icreisan ases? 8 I 

are the usual quant 

atmo<*ph' «•« oxypen 

Whmt nitropen * 
i does sulphur 'M< ir in nature? be eoauncr< 

.ned? 828. In what forms does it com • 29. 



376 QUESTIONS. 

Give the properties and uses of sulphur. 330. Name the modifications 
of sulphur. 331. Under what conditions will rhombic sulphur pass into 
the other forms? 332. Of what use is plastic . sulphur in the arts? 
333. Where is sulphureted hydrogen found ? 334. Explain the method 
of liberating this gas. 335. Give its properties and uses. 336. Of what 
use is sulphur chloride in the arts ? 337. How may sulphur unite with 
oxygen ? 338. When is sulphurous oxide liberated ? 339. For what is 
SO a used ? 340. What are the sulphites ? 341. Give the composition 
of sulphuric oxide. 342. How early was sulphuric acid known ? 343. 
How is it manufactured ? 344. What are the properties of this acid ? 
345. State the phenomena which occur when sulphuric acid and water are 
mixed together. 346. What can you state of fuming sulphuric acid ? 
34V. What do the words selenium and tellurium mean? 348. What 
important property has selenium ? 

CHAPTER XVI.— Carbon, Silicon. 

349. What are the allotropic forms of carbon ? 350. Which is the 
purest form? 351. State what you can of the diamond. 352. Give the 
properties of graphite. 353. How is charcoal obtained ? 354. Tell its 
uses. 355. Is it an antiseptic ? 356. What is lamp-black ? 357. How 
is carbon monoxide produced ? 358. How is mineral coal believed to 
have been formed ? 359. What is coke ? 360. What is the character 
of its flame? 361. Give the composition of carbon monoxide. 362. 
How is carbonic acid prepared ? 363. How can you prove that CO2 is 
not a supporter of combustion, and that it is heavier than air ? 364. 
What experiment shows that carbon dioxide is in expired breath? 
365. What is soda-water ? 366. Give the properties and uses of carbon 
disulphide. 367. What is the symbol of cyanogen ? 368. Where is 
prussic acid found ? 369. How does the chemist use the term combus- 
tion ? 370. State what is said of the gradation of affinities between 
oxygen and the elements of combustible bodies. 371. Show how ex- 
plosive combustion takes place. 372. What is eremacausis ? 373. What 
does intensity of heat depend upon ? 374. What is a spontaneous com- 
bustion? 375. How does chemical action produce heat? 376. What 
kind of substances produce flame ? 377. State the conditions of illumi- 
nation. 378. Describe the compound blow-pipe. 379. What constitutes 
the Drummond light? 380. How does the candle burn? 381. Give a 
statement of the structure of flame. 382. How may the constant pres- 
ence of free carbon in the flame be proved ? 383. Upon what does the 
amount of light produced depend ? 384. What is the principle on 
which the safety-lamp is constructed? 385. What modifications has 
silicon ? 386. Give the composition of silica. 387. It forms the bulk 



3 



. * 



of what : 38* Wh.it i- :!. inn of tin- opal 1 389. 

Iln\\ i> 
I 

CHAPTSB X \ 1 1 

ff ha! WWt I 

limn! W 

B 

I 
pota 

Bon 

salt 

d naphtha 

i 
ha,- poUrnlnni carbonate! 112. What Ki Mtarmtus? 418. What is 
potassium nit 

1 l B, What do 'h- | 

CHAPTBfi Win- 1 mm. 

i- milk <-f lin 
mortar DM 
com posit: 

what are 1 

ertie* and uses of magnesium ? 

are it? properties? 
folphau 

cadmium. 



378 QUESTIONS. 

CHAPTER XX.— Thallium, Lead. 

440. What is the spectrum of thallium? 441. What is galena? 
442. Give the uses of lead. 443. What danger may arise from the use 
of lead pipe ? 444. The presence of what salts in the water protects 
the lead against its corroding action ? 445. Give properties of lead 
monoxide. 446. How is white lead obtained ? 447. How are paints 
prepared ? 448. Give properties of lead acetate. 

CHAPTER XXL— Copper, Mercury, Silver. 

449. In what forms is copper found in nature ? 450. What are the 
properties of metallic copper ? 451. What is verdigris ? 452. What pre- 
caution should be taken with copper utensils in the kitchen ? 453. What 
can you say of the alloys of copper ? 454. Give the preparation and uses 
of cupric oxide. 455. Of cupric sulphate. 456. What is Paris-green, and 
what are its properties ? 457. State the properties and uses of mercury. 
458. What are amalgams ? 459. In what important chemical discovery 
was mercuric oxide used ? 460. What is the antidote for mercuric 
chloride? 461. Give the properties of calomel. 462. Under what name 
is mercuric sulphide sold ? 463. How does silver occur in nature ? 
464. Describe cupellation. 465. Tell the chief properties and uses of sil- 
ver. 466. What is lunar caustic, and what are its properties ? 467. How 
may stains of indelible ink be removed ? 468. For what are the haloid 
salts of silver remarkable ? 469. How are photographs taken ? 470. How 
is the picture developed on the negative? 471. How are the prints 
made? 472. Give some idea of the varying effects of colored lights. 
473. Give some of the applications of photography to astronomy. 

CHAPTER XXII. — The Cerium Group and the Aluminum Group. 

474. What is the quantivalence of the members of the cerium group ? 
475. How does aluminum occur in nature ? 476. How has electricity 
been applied in extracting it ? 477. What are its properties ? 478. What 
are the ruby, sapphire, and topaz ? 479. What are emery and corun- 
dum? 480. Describe alum and tell its uses ? 481. What is burnt alum ? 
482. Name some minerals that are aluminum silicates. 483. How is 
porcelain made? 484. How are earthenware and common pottery 
glazed ? 485. What gives the red color to coarse pottery and bricks ? 

486. What interest has indium in respect to the Periodic Classification? 

487. In what peculiar way does melted gallium behave ? 



qi BsnoNa 

iii win; win — v kkl. 

4SS. I L89. For wbtA k the Mack 

le used? ninm perman- 

ii Kfl cast- 
! Ascribe the j i ibtainmg 

I B i w ■■■ if the • bm iit.it i< m proa u far 

l>or- 
ties of iron. 497. What is the • tanl jarring on w r o u ght 

ipialiiy belongs "iiiy t.. iron, 
. ami sod! the origin <»f the term pig-iron. 

able in tin 

Which i- the most ralnabls Iron-ore! r>04. 

.iii-i oom- 
<»f greens I the 

wee of nickel. 

;; \\IV-('!ii;,imi; I 

' v. • , , the 
uses of «■' ■ ramie anhydride in 

a marked de_ and oaee <>f potassium 

dichr<»m:r being assigned t<> 

molybdenum? -t.-n. :, 11- florwhaJ 

sodium uranate used ? 

CHAPTBH XW-Tr. 

kin | BIO, Wli.it .: the 

peculiar crackling sound given I In whei two 

way- .Ms. Wl 

619. 
521. What elements an* 

• II 

Chi what proportir 1 1 

scribe it- use in safety-plugs. 



380 ' QUESTIONS. 

528. What are the associates of platinum ? 529. What acid acts upon it? 
530. For what is it used? 531. What power has spongy platinum? 
532. How may platinic chloride be obtained ? 

CHAPTER XXVIIL— The Methane Derivatives. 

533. Give some of the characteristics of the carbon compounds. 
534. What are homologous series ? 535. Describe marsh-gas. 536. How 
is coal-gas made ? 537. How are isomeric hydrocarbons believed to differ 
in constitution ? 538. Describe the paraffins. 539. How is fractional dis- 
tillation performed? 540. Where is petroleum found? 541. What is 
kerosene ? 542. What is regarded as a safe " flashing-point " for a 
paraffin-oil? 543. For what is paraffin used? 544. How is "water- 
gas " made ? 545. Describe ethylene. 546. Why is acetylene of special 
interest ? 547. What is chloroform ? 548. How are alchohols derived 
from paraffin ? 549. From what is wood-spirit obtained ? 550. Give the 
formula for common alcohol. 551. What are its properties ? 552. When 
is wine said to be sparkling ? 553. Give what information you can re- 
garding lager-beer, ale, and porter. 554. How does brandy differ from 
wine? 555. What is fusel-oil? 556. How are ethers regarded by the 
chemist ? 557. Describe ethyl ether. 558. What is " sweet spirits of 
niter"? 559. What is the constitution of the glycols? 560. For what 
is glycerin used? 561. How is nitro-glycerin exploded? 562. What 
are amines ? 563. How are aldehydes related to alcohols and acids ? 
564. What are the properties of acetic aldehyde? 565. Give composi- 
tion and properties of chloral ? 566. Mention some of the carbohydrates. 
567. What are the glucoses ? 568. Give formula and properties of cane- 
sugar. 569. What is lactose used for ? 570. How does starch differ 
from sugar in its composition? 571. What are the properties and uses 
of starch ? 572. How may commercial starch be converted into dextrin ? 
573. Mention substances isomeric with starch. 574. From what may 
cellulose be obtained ? 575. Give the uses of cellulose. 576. How may 
cellulose be converted into pyroxylin? 577. How does the explosive 
force of pyroxylin compare with that of gunpowder ? 578. What is col- 
lodion ? 579. What distinction is made between the terms fermentation 
and putrefaction ? 580. What is the exciting cause of fermentation ? 
581. Give examples of ferments and fermentable bodies. 582. What is 
said of yeast? 583. Mention the different modes of fermentation. 584. 
What are the products of vinous fermentation ? 585. What is diastase? 
586. To what does vinous fermentation, if not checked, pass? 587. 
What chemical changes take place in the making of vinegar? 588. 
What is the composition of acetic acid ? 589. From what is formic acid 
obtained ? 590. Give method of preparing butyric acid, and its proper- 



QUESTIONS 

ties. 591. ' r the 

ehemlstr} of bq What i- th< 

oxalic 

.\i\ .- r 

does the benzene moleonle differ from the paraffin molecul wimi 

is the 

'■'. • two kind 
. tnd for wli..t \i it u- Qire composition of 

benzoic :. (;j vc his alicylio 

oharacterii 
i I -'.l". wi.ni chemical ehai 
produi Ll, Wli.it Lb alixarin! 611 Whal ifl oil of 

mphor obtained I 61 1. What Ifl the 
- 

OHAFTBB \\ \ — < 

r>!7. w of litmus, 

the orga 
[be the alkaloid contained 
in tob: Wh.it i: principle of opium ! 

I what 

tlii- alkaln I tTOUfl 

the libominoids. 
in and 

uinin. 
683. What is sr 
the rod 

• 



INDEX, 



A 
\ 

of , 

bor 






; 









ist. 



' 



. l 75. 
BoIplmroaB, 1 7 1. 

thio-ffilpfa 

-titu- 

1 I. 
Aftiiiit 

\ 

. 

\ 
\ 



384 



INDEX. 



Aluminates, 256. 

Aluminum in the sun, 61 ; extrac- 
tion and properties j 253 ; alloys, 
255 ; oxide, 255 ; hydrate, 256 ; 
sulphates, 256 ; silicates, 257. 

Amalgamation process, 246. 

Amalgams, 244. 

Amethyst, 204. 

Amides, 328. 

Amines, 308. 

Ammonia, 127 ; water, 129; in the 
air, 166 ; substituted, 308. 

Ammonium, 130; hydrate, 130; 
chloride, 131 ; nitrate, 132. 

Amorphous substances, 20. 

Amygdalin, 337. 

Amylose group, 314. 

Analysis, 63. 

Anhydride, 87. 

Anilin, 333 ; black, 334. 

Anthracene, 343. 

Anthracite, 187. 

Anthraquinone, 343. 

Antimony, 1 44 ; oxides, 144 ; chlo- 
rides, 145 ; sulphides, 145; "but- 
ter of," 145. 

Antiseptics, 336. 

Ant ozone, 154. 

Aqua-fortis, 134. 

Aqua regia, 136, 284. 

Arabin, 316. 

Aromatic hydrocarbons, 330. 

Arsenic, 141 ; test for, 142 ; oxides 
and acids, 143 ; sulphides, 143. 

Arseniureted hydrogen, 141. 

Arsines, 309. 

Artiads, 79. 

Asparagin, 328. 

Astrology, influence on chemistry, 
101. 

Atmosphere, composition, 164; hu- 
midity, 165 ; carbon dioxide in, 
165 ; relation to living world, 
166. 

Atom in chemistry, 71. 

Atomic heat, 93. 
theory, 69. 

weights tested by the periodic 
classification, 101. 

Atomicity, 76, 79. 

Atropine, 355. 

Avogadro's law, 91. 

Axes of crystals, 24. 



B 

Baking-powder, 217. 
Balance, 4. 
Balsams, 346. 
Barium, 231. 

Bases, constitution, 84 ; quantiva- 
lence, 86 ; names, 1 04 ; organic, 
353. 
Basicity, 86. 
Bassorin, 317. 
Battery, galvanic, 42. 
Beer, 305. 

Benzene, 331 ; ring, 330. 
Benzine, 299, 331. 
Benzoic acid, 338. 

aldehyde, 337. 
Benzol, 331. 
Benzyl alcohol, 337. 
Beryl, 205, 232. 
Beryllium, 96, 232. 
Bessemer process, 267; spectro- 

scope in, 59. 
Binary compounds, 83. 

theory, 74. 
Birch, oil of, 339. 
Biscuit-ware, 258. 
Bismuth, 282. 
Bitter principles, 349. 
Blast-furnace, 263. 
Bleaching by chlorine, 119 ; by sul- 
phurous oxide, 174. 

powder, 227. 
Blomary process, 265. 
Blood, 359. 

Blow-pipe, compound, 197. 
Bodies, 3. 
Boiling, 31. 

point on thermometer, 29 ; of 
liquids, 32. 
Bonds, 77 ; control combination, 78 ; 

mode of linking, 80. 
Borax, 147. 
Boric acid, 145. 
Borneol, 345. 

Boron, 96, 145 ; in classification, 
126. 

trioxide, 147. 
Brandy, 305. 
Brass, 242. 
Bricks, 259. 
Brimstone, 168. 
Britannia metal, 144, 279„ 



INDEX 






« 
I 

226; haloid 
I 
light, 

I 

. 1 V 
cavities, !•'•. 

i 



•itcs, 311. 
< 181; 

:aa, 188. 

I 






II 



( Vm.ni.itio; 

I thrill. <»n 

I 

Chemical action, conditio • 

I ; in tin. l, 

i ogth, 
pel Ltioo i" 1 1 
1 
malka] 

88; organic, 

in- 

Chloro] 

I 
I 

1 
1 
I 

ic, 95. 

I 



386 



INDEX. 



Colophony, 345. 

Coloring matters, vegetable, 351 ; 
animal, 352. 

Combination by volume, 94. 

Combining capacity, variable, 75. 
proportions, 68. 

Combustion, 194 ; rapid, 195 ; slow, 
195; spontaneous, 196; heat of, 
39, 196 ; how the candle burns, 
198; order, 199. 

Compounds, 63. 

Condensation of gases, 36. 

Coniine, 353. 

Copper, 241 ; compounds, 242. 

Copperas, 272. 

Corrosive sublimate, 244. 

Corundum, 255. 

Creatine, 356. 

Creatinine, 356. 

Creosote, 337, 

Oresol, 335. 

Cryophorus, 33. 

Crystals, 20 ; in nature, 21 ; quartz, 
21 ; imperfect, 21, 23 ; from solu- 
tion, 21 ; by fusion, 22 ; by sub- 
limation, 22 ; repair of, 23 ; 
forms of, 24 ; derived forms, 26. 

Crystallization, 20 ; in the solid 
state, 22 ; effect of jarring, 23 ; 
expansion from, 23 ; heat and 
light from, 23 ; systems, 25. 

Crystalloids, 18, 20 ; separated 
from solution, 20. 

Cupellation, 246. 

Curcumin, 351. 

Cyanogen, 193. 

Cyano-paraffins, 302. 

Cymene, 344. 

D 

Daguerreotypes, 251. 

DanielPs hygrometer, 34. 

Decimeter, 5. 

Definite proportions, law of, 68. 

Deliquescence, 163. 

Density, 4 ; calculation of, 6 ; of 

vapors, maximum, 35. 
Deodorants, 336. 
Dew-point, 34. 
Dextrin, 316. 
Dextrose, 311, 316. 
Diamond, 181. 
Diastase, 321. 



Didymium, 253. 

Diffusion, 16 ; of gases, 16 ; of 

liquids, 17 ; of solids in liquids, 

18; of gases in liquids, 19; of 

gases in solids, 20. 
Diinetric crystals, 25. 
Disinfectants, 120, 336. 
Displacement, 117, 128. 
Distillation, 35 ; destructive, 293 ; 

fractional, 296. 
Dobereiner's lamp, 112. 
Draper's investigations of spectra, 

54, 
Drummond light, 198. 
Dualism, 74. 
Dulcite, 308. 
Durene, 331. 
Dutch liquid, 302. 
Dynamical theory of heat, 39. 
Dynamite, 308. 

E 

Earthenware, 259. 

Ebonite, 347. 

Efflorescence, 163. 

Electric light for spectrum work, 
58. 

Electricity produced by chemical 
action, 40 ; intensity, 42 ; quan- 
tity, 42. 

Electro-deposition, 44. 

Electro-motive force, 41. 

Electrodes, 41. 

Electrolysis, 43. 

Elements, positive and negative, 43 
in the sun, 60 ; in the stars, 61 
defined, 63 ; in the free state, 80 
organic, 89 ; classification, 95 
names, 102. 

Emerald, 205, 232. 

Emery, 255. 

Epsom salts, 233. 

Equations, 105. 

Equivalent proportions, 69. 

Erbium, 253. 

Erythrite, 308. 

Etching glass, 115. 

Ethane, 293. 

Ethers, 306. 

Ethyl nitrite, 306. 

Ethylene, 300 ; chloride, 301. 

Evaporation, 32 ; cooling effect 
33. 






887 






ttccharou 

I 

■ 

: 
I 

l 
I 



i 



. 



I 1 5 

I 

811. 

I 

i 

1 1. 

■ 

I 

II 

114 

I 



388 



INDEX. 



Hydrocyanic acid, 193. 
Hydrofluoric acid, 115. 
Hydrogen in the sun, 60 ; acid, 86 ; 

preparation and properties, 107 ; 

chemical use, 113; phosphureted 

140 ; arseniureted, 141 ; dioxide, 

163 ; sulphureted, 170. 
acids, 84. 
Hydrogenium, 113. 
Hydrometer, 10. 
Hydrosulphuric acid, 170. 
Hydroxyl, S3. 
acids, 83. 
Hygrometer, 34. 
Hyoscine, 355. 
Hyoscy amine, 355. 



-ic and -ous, meaning, 103, 104. 

Ignition, point of, 195 ; sponta- 
neous, 196. 

India-rubber, 347. 

Indican, 348. 

Indigo-blue (indigotin), 348. 

Indium, 259. 

Indol, 347. 

Induction, chemical, 66. 

Ink, 340. 

Inulin, 316. 

Iodides, 126. 

Iodine, 125. 

Iodoform, 302. 

Iridium, 287. 

Iron in the sun, 61; occurrence, 
262 ; wrought, 265, 268 ; cast, 
265, 269; puddling, 266; prop- 
erties, 267 ; passive, 268 ; uses, 
270 ; oxides, chloride, 271 ; sul- 
phide, sulphate, carbonate, cya- 
nides, 272. 

Isinglass, 357. 

Isomeric hydrocarbons, 294. 

Isomerism, 89. 

Isometric crystals, 25. 

Isomorphism, 27.' 



Jasper, 204. 
Jet, 187. 



K 



Kaolin, 258. 
Kelp, 215, 220. 



I Keratin, 363. 
Kerosene, 297 ; testing, 298. 
Kyanizing, 245. 



Lactic acid, 326. 

Lactose, 314. 

Laevulose, 311. 

Lager-beer, 305. 

Lamp-black, 186. 

Lanthanum, 253. 

Lapis lazuli, 258. 

Laughing-gas, 133. 

Law, 1. 

Lead, black, 183. 

Lead, 237 ; oxides, 239 ; basic car- 
bonate, 239 ; acetate, 240 ; tests 
for, 240. 

Leather, 341. 

Leblanos process, 215. 

Legumin, 361. 

Leukanilin, 334. 

Light, chemical effects, 47; analysis, 
48 ; white from colored rays, 49. 

Lignite, 187. 

Lime, 225 ; water, 226 ; chloride of, 
227 ; stone, 229. 
ball, 198. 

Liquefaction, 30; consumes heat, 
31 ; of gases, 36. 

Liquids, expansion, 28. 

Liquors, fermented, 304 ; distilled, 
305. 

Liter, 5. 
; Litharge, 239. 
j Lithium, 96, 210. 
| Litmus, 352. 
[ Loadstone, 271. 
; Luminous paint, 231. 
j Lunar caustic, 248. 

Lupulin, 350. 

M 

Madder, 343. 

Magnesium, 232 ; compounds, 233. 

Magnetite, 271. 

Malachite, 241. 

Malic acid, 327. 

Malt, 305. 

Maltose, 314. 

Manganese, 261. 

Mannite, 308. 

Marsh gas, 291. 









\ . 

i the 
If 

. 71 ; 



- 






N 

N 
in t! 

101. 



to I 





















' 






390 



INDEX. 



uses, 100; metals in, 106; place 
of indium in, 259, 

Perissads, 79. 

Peru balsam, 337. 

Petroleum, 297. 

Pewter, 279. 

Phenols, 334. 

Phenomena, 1. 

Phenyl, 332 ; amine, 333 ; alcohol, 
335. 

Phlogiston, 73. 

Phosphines, 309. 

Phosphoric acid, 139. 
anhydride, 139. 

Phosphorus, 136 ; compounds, 138. 

Phosphureted hydrogen, 140. 

Photography, 249 ; celestial, 252. 

Photophone, 180. 

Photosphere, 58, 61. 

Physical properties, relation to 
atomic weights, 100. 

Physics, 1 ; chemical, 2. 

Picric acid, 333. 

Picrotoxin, 350. 

Pitch, coal-tar, 330. 

Plaster of Paris, 228. 

Platinum, 286 ; action on hydro- 
gen, 112. 

Plumbago, 183. 

Pneumatic trough, 109. 

Poles of electric circuit, 41. 

Polymeric compounds, 90. 

Porcelain, 258 ; Reaumur's, 209. 

Porositv, 12. 

Porter, "305. 

Positive elements, 43. 

Potash, 221 ; caustic, 219. 

Potassa, 219. 

Potassium, 218; oxide, 219; hy- 
drate, 219; chloride, 220; car- 
bonate, 220 ; acid carbonate, 221 ; 
nitrate, 221; chlorate, 223; cy- 
anide, 224 ; permanganate, 262. 

Pottery, 258. 

Precipitation, 20. 

Prefixes and suffixes, meaning, 103, 
104. 

Propane, 294. 

Proportions, definite, 68; equiva- 
lent, 69 ; multiple, 68. 

Proteids, 357. 

Prussian-blue, 273. 

Prussic acid, 193. 



Ptomaines, 364. 
Pumice-stone, 258. 
Purple, 352. 

of Cassius, 286. 
Putrefaction, 318. 
Pyridine, 342. 
Pyrites, 272. 
Pyrogallol, 337. 
Pyroxylin, 317. 

Q 

Quanti valence, 76 ; modes of ex- 
pressing, 77; of molecules, 80; 
varying, 79. 

Quartz, 203 ; smoky, 204 ; crystals, 
21. 

Quicksilver, 243. 

Quinidine, 354. 

Quinine, 354. 

Quinoline, 342. 

R 

Radiant forces, 44. 

Radicals, compound, 82 ; quanti va- 
lence, 82 ; names, 102 ; simple, 
82. 

Railway-train illustrates nature of 
heat, 39. 

Reactions, how represented, 105. 

Reaumur's porcelain, 209. 
thermometer, 30. 

Reducing agent, 113. 

Refraction of invisible rays, 45. 

Refrangibility, differing, 45, 49. 

Rennet, action of, 319. 

Resins, 346. 

Rhigolene, 298. 

Rhodium, 287. 

Rochelle salt, 328. 

Rock-oil, 297. 

Rosanilin, 334. 

Rosin, 345. 

Rubidium, 224. 

Ruby, 255. 

Rum, 305. 

Ruthenium, 287. 

S 
Saccharin, 338. 
Saccharose group, 312. 
Safety-lamp, 201. 
Sal-ammoniac, 131. 
Sal-prunelle, 222. 






391 



Sali 
Sah>. 



- 17. 

18. 

Soda, ca<. 

-w.v 
Sodium, I 

S*»l.«nin. M9. 

19. 

Specific p 
tancr, 1 1 . 



I ; in 

urn, three kinds, 15 ; - 

urin_. VJ ; d : <li>- 

lim ;is a 

. 

S 

101. 

Stanni< 
Starch, 81 i. 

•i, 61. 
, latent hi 

otro- 

Btrycl ! 

titution the ry, 71. 

112; milk, 

Snlpn [pitated by ralpho- 

Solpbo-eolpb . 179. 

Snlphor, 167 ; chloi 

. : oxide, I . 

Solpfa 

:n:ucnces f 



i 



392 



INDEX. 



Tar, coal, 293 ; products, 330. 

Tartar, 327; cream of, 328. 

Tartaric acid, 327. 

Tartrate, potassium-sodium, 328. 

Tea, 356. 

Tele-spectroscope, 60. 

Tellurium, 180. 

Temperature, 28. 

Terbium, 253. 

Terebenthene, 345. 

Tetragonal crystals, 25. 

Thallium, 236. 

Theine, 356. 

Theobromine, 356. 

Theories, early, 73. 

Thermometer, 28; Celsius's, 30; 
centigrade, 30 ; Fahrenheit's, 30 ; 
Reaumur's, 30 ; scales, 29. 

Thermotics, 27. 

Thio- sulphuric acid, 179. 

Thorium, 281. 

Thorn-apple, 355. 

Tin, 278; plate, foil, 279; com- 
pounds, 280 ; crystals, 22. 

Titanium, 280. 

Thymol, 344. 

Tolu balsam, 337. 

Toluene, 332. 

Toluidin, 333. 

Topaz, 204, 255. 

Triclinic crystals, 25. 

Trimetric crystals, 25. 

Trinitro-phenol, 333. 

Tungsten, 277. 

Turnbull's blue, 273. 

Turpenes, 344, 

Turpentine, 345. 

Type-metal, 144, 238. 

Types, chemical, 75. 

U 

Ultramarine, 258. 
Uranium, 278. 
Urea, 328, 363. 
Uric acid, 364. 



Valency, 77. 
Vanadium, 282. 



Vanillin, 338. 

Vaporization, 32. 

Vapors, elastic force or tension, 35 ; 

maximum density, 35. 
Vegetable parchment, 317. 
Vegetation dependent on light, 47. 
Verdigris, 242. 
Vermilion, 245. 
Vinegar, 321. 
Vital force, 88, 289. 
Vitriol, blue, 243. 

green, 272. 

oil of, 175. 

white, 235. 
Volatile substances, 32. 
Voltaic electricity, 40. 

pile, 41. 
Volume, 3 ; measurement, 5. 
Volumes, combining, 94. 

W 

Water, electrolysis of, 43 ; occur- 
rence and properties, 154, 163 5 
varieties, 160 ; action on lead» 
237. 

of constitution, 87. 
of crystallization, 87. 

Water-gas, carbon monoxide in, 188. 

Weight, 4. 

Weights and measures, metric, 5 ; 
standard, 5. 

Whiskv, 305. 

Wines,' 304. 

Wintergreen, oil of, 339. 

Wood-spirit, 303. 

Woulfe's bottles, 129. 

Wourali, 355. 



Xvlene, 331. 



Yeast, 320. 
Yttrium, 253. 



Zinc, 233 ; compounds, 235. 
Zirconium, 281. 



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